feat(telegram,game): single bot + per-user variant preferences

Collapse the two per-language Telegram bots into one unified bot and
replace language-based variant gating with explicit per-user variant
preferences.

- Telegram: one bot; drop service_language and the supported_languages
  set everywhere (DB, account, auth, FlatBuffers Session wire, gateway,
  connector proto). The single bot renders chat and out-of-app push in
  the recipient's preferred_language; remove the game-language push
  routing override (notify Intent.Language / push Event.language).
- Preferences: new accounts.variant_preferences (text[], DB default
  {erudit_ru}, CHECK non-empty + subset of the three variants). Gates
  the New Game picker, vs-AI and the friend invitation the player
  creates, enforced server-side (HTTP 400 otherwise); an invited friend
  may still accept any variant. Edited on the Settings screen; variants
  are Erudit-first everywhere.
- Admin: drop the per-bot language selectors (broadcast / send-to-user)
  and the feedback channel_lang column/field.
- Env/CI: collapse TELEGRAM_BOT_TOKEN_{EN,RU}, TELEGRAM_GAME_CHANNEL_ID_{EN,RU},
  VITE_TELEGRAM_LINK{,_EN,_RU} and VITE_TELEGRAM_GAME_CHANNEL_NAME_{EN,RU}
  to single unsuffixed names; drop GATEWAY_DEFAULT_SUPPORTED_LANGUAGES.
- Docs updated (ARCHITECTURE, FUNCTIONAL + _ru, platform/telegram, gateway,
  backend, ui, UI_DESIGN, PRERELEASE).

The migration squash is deferred to a follow-up PR.

gateway/internal/transcode/encode.go

@@ -13,38 +13,17 @@ import (
 // created before the table that references it, and no two tables/vectors are
 // under construction at once.
 
-// buildSupportedLanguagesVector creates the Session.supported_languages [string]
-// vector from langs. FlatBuffers is built bottom-up, so the caller must invoke this
-// (which itself creates the element strings) before SessionStart and with no table
-// under construction.
-func buildSupportedLanguagesVector(b *flatbuffers.Builder, langs []string) flatbuffers.UOffsetT {
-	offsets := make([]flatbuffers.UOffsetT, len(langs))
-	for i, lang := range langs {
-		offsets[i] = b.CreateString(lang)
-	}
-	fb.SessionStartSupportedLanguagesVector(b, len(langs))
-	for i := len(offsets) - 1; i >= 0; i-- {
-		b.PrependUOffsetT(offsets[i])
-	}
-	return b.EndVector(len(langs))
-}
-
-// encodeSession builds a Session payload. supportedLangs is the service's set of
-// offered game languages, which the UI gates the New Game variant choice by.
-func encodeSession(s backendclient.SessionResp, supportedLangs []string) []byte {
+// encodeSession builds a Session payload.
+func encodeSession(s backendclient.SessionResp) []byte {
 	b := flatbuffers.NewBuilder(128)
 	token := b.CreateString(s.Token)
 	uid := b.CreateString(s.UserID)
 	name := b.CreateString(s.DisplayName)
-	svcLang := b.CreateString(s.ServiceLanguage)
-	langs := buildSupportedLanguagesVector(b, supportedLangs)
 	fb.SessionStart(b)
 	fb.SessionAddToken(b, token)
 	fb.SessionAddUserId(b, uid)
 	fb.SessionAddIsGuest(b, s.IsGuest)
 	fb.SessionAddDisplayName(b, name)
-	fb.SessionAddSupportedLanguages(b, langs)
-	fb.SessionAddServiceLanguage(b, svcLang)
 	b.Finish(fb.SessionEnd(b))
 	return b.FinishedBytes()
 }
@@ -74,6 +53,7 @@ func encodeProfile(p backendclient.ProfileResp) []byte {
 	if p.Banner != nil {
 		banner = encodeBanner(b, *p.Banner)
 	}
+	prefs := buildStringVector(b, p.VariantPreferences, fb.ProfileStartVariantPreferencesVector)
 	fb.ProfileStart(b)
 	fb.ProfileAddUserId(b, uid)
 	fb.ProfileAddDisplayName(b, name)
@@ -86,6 +66,7 @@ func encodeProfile(p backendclient.ProfileResp) []byte {
 	fb.ProfileAddAwayStart(b, awayStart)
 	fb.ProfileAddAwayEnd(b, awayEnd)
 	fb.ProfileAddNotificationsInAppOnly(b, p.NotificationsInAppOnly)
+	fb.ProfileAddVariantPreferences(b, prefs)
 	if p.Banner != nil {
 		fb.ProfileAddBanner(b, banner)
 	}
@@ -147,10 +128,8 @@ func encodeBlockStatus(s backendclient.BlockStatusResp) []byte {
 
 // encodeLinkResult builds a LinkResult payload. A switched-session token
 // (a guest initiator whose durable counterpart won) is carried as a nested Session
-// for the client to adopt; it is omitted otherwise. supportedLangs is the variant
-// gating set for that switched session — the link flows run on the web, so it is the
-// gateway's default (non-platform) set.
-func encodeLinkResult(r backendclient.LinkResultResp, supportedLangs []string) []byte {
+// for the client to adopt; it is omitted otherwise.
+func encodeLinkResult(r backendclient.LinkResultResp) []byte {
 	b := flatbuffers.NewBuilder(256)
 	status := b.CreateString(r.Status)
 	secID := b.CreateString(r.SecondaryUserID)
@@ -161,13 +140,11 @@ func encodeLinkResult(r backendclient.LinkResultResp, supportedLangs []string) [
 		token := b.CreateString(r.Token)
 		uid := b.CreateString(r.Profile.UserID)
 		name := b.CreateString(r.Profile.DisplayName)
-		langs := buildSupportedLanguagesVector(b, supportedLangs)
 		fb.SessionStart(b)
 		fb.SessionAddToken(b, token)
 		fb.SessionAddUserId(b, uid)
 		fb.SessionAddIsGuest(b, r.Profile.IsGuest)
 		fb.SessionAddDisplayName(b, name)
-		fb.SessionAddSupportedLanguages(b, langs)
 		sess = fb.SessionEnd(b)
 	}
 	fb.LinkResultStart(b)

gateway/internal/transcode/transcode.go

@@ -89,20 +89,14 @@ type TelegramValidator interface {
 // NewRegistry builds the slice's message-type catalog over the backend client.
 // The Telegram auth op is registered only when a validator is supplied (the
 // connector is configured); otherwise auth.telegram is simply unknown.
-// defaultLanguages is the New Game variant gating set placed on the Session for
-// non-platform logins (web / email / guest) and on a switched link session; an
-// empty argument falls back to all languages (matching the config default).
-func NewRegistry(backend *backendclient.Client, tg TelegramValidator, defaultLanguages ...string) *Registry {
-	if len(defaultLanguages) == 0 {
-		defaultLanguages = []string{"en", "ru"}
-	}
+func NewRegistry(backend *backendclient.Client, tg TelegramValidator) *Registry {
 	r := &Registry{ops: make(map[string]Op)}
 	if tg != nil {
 		r.ops[MsgAuthTelegram] = Op{Handler: authTelegramHandler(backend, tg)}
 	}
-	r.ops[MsgAuthGuest] = Op{Handler: authGuestHandler(backend, defaultLanguages)}
+	r.ops[MsgAuthGuest] = Op{Handler: authGuestHandler(backend)}
 	r.ops[MsgAuthEmailReq] = Op{Handler: authEmailRequestHandler(backend), Email: true}
-	r.ops[MsgAuthEmailLogin] = Op{Handler: authEmailLoginHandler(backend, defaultLanguages), Email: true}
+	r.ops[MsgAuthEmailLogin] = Op{Handler: authEmailLoginHandler(backend), Email: true}
 	r.ops[MsgProfileGet] = Op{Handler: profileHandler(backend), Auth: true}
 	r.ops[MsgBlockStatus] = Op{Handler: blockStatusHandler(backend), Auth: true}
 	r.ops[MsgGameSubmitPlay] = Op{Handler: submitPlayHandler(backend), Auth: true}
@@ -130,7 +124,7 @@ func NewRegistry(backend *backendclient.Client, tg TelegramValidator, defaultLan
 	r.ops[MsgFeedbackGet] = Op{Handler: feedbackGetHandler(backend), Auth: true}
 	r.ops[MsgFeedbackUnread] = Op{Handler: feedbackUnreadHandler(backend), Auth: true}
 	registerSocialOps(r, backend)
-	registerLinkOps(r, backend, tg, defaultLanguages)
+	registerLinkOps(r, backend, tg)
 	return r
 }
 
@@ -164,21 +158,21 @@ func authTelegramHandler(backend *backendclient.Client, tg TelegramValidator) Ha
 		if err != nil {
 			return nil, err
 		}
-		sess, err := backend.TelegramAuth(ctx, user.ExternalID, user.LanguageCode, user.Username, user.FirstName, user.ServiceLanguage)
+		sess, err := backend.TelegramAuth(ctx, user.ExternalID, user.LanguageCode, user.Username, user.FirstName)
 		if err != nil {
 			return nil, err
 		}
-		return encodeSession(sess, user.SupportedLanguages), nil
+		return encodeSession(sess), nil
 	}
 }
 
-func authGuestHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func authGuestHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, _ Request) ([]byte, error) {
 		sess, err := backend.GuestAuth(ctx)
 		if err != nil {
 			return nil, err
 		}
-		return encodeSession(sess, supportedLangs), nil
+		return encodeSession(sess), nil
 	}
 }
 
@@ -192,14 +186,14 @@ func authEmailRequestHandler(backend *backendclient.Client) Handler {
 	}
 }
 
-func authEmailLoginHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func authEmailLoginHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsEmailLoginRequest(req.Payload, 0)
 		sess, err := backend.EmailLogin(ctx, string(in.Email()), string(in.Code()))
 		if err != nil {
 			return nil, err
 		}
-		return encodeSession(sess, supportedLangs), nil
+		return encodeSession(sess), nil
 	}
 }
 

gateway/internal/transcode/transcode_link.go

@@ -22,15 +22,13 @@ const (
 
 // registerLinkOps adds the linking & merge operations. The telegram ops need the
 // connector's Login Widget validator, so they are registered only when tg is set.
-// supportedLangs is the variant gating set for a switched link session (the link
-// flows run on the web, so the gateway default set).
-func registerLinkOps(r *Registry, backend *backendclient.Client, tg TelegramValidator, supportedLangs []string) {
+func registerLinkOps(r *Registry, backend *backendclient.Client, tg TelegramValidator) {
 	r.ops[MsgLinkEmailRequest] = Op{Handler: linkEmailRequestHandler(backend), Auth: true, Email: true}
-	r.ops[MsgLinkEmailConfirm] = Op{Handler: linkEmailConfirmHandler(backend, supportedLangs), Auth: true, Email: true}
-	r.ops[MsgLinkEmailMerge] = Op{Handler: linkEmailMergeHandler(backend, supportedLangs), Auth: true, Email: true}
+	r.ops[MsgLinkEmailConfirm] = Op{Handler: linkEmailConfirmHandler(backend), Auth: true, Email: true}
+	r.ops[MsgLinkEmailMerge] = Op{Handler: linkEmailMergeHandler(backend), Auth: true, Email: true}
 	if tg != nil {
-		r.ops[MsgLinkTelegram] = Op{Handler: linkTelegramHandler(backend, tg, false, supportedLangs), Auth: true}
-		r.ops[MsgLinkTelegramMerge] = Op{Handler: linkTelegramHandler(backend, tg, true, supportedLangs), Auth: true}
+		r.ops[MsgLinkTelegram] = Op{Handler: linkTelegramHandler(backend, tg, false), Auth: true}
+		r.ops[MsgLinkTelegramMerge] = Op{Handler: linkTelegramHandler(backend, tg, true), Auth: true}
 	}
 }
 
@@ -44,31 +42,31 @@ func linkEmailRequestHandler(backend *backendclient.Client) Handler {
 	}
 }
 
-func linkEmailConfirmHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func linkEmailConfirmHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsLinkEmailConfirm(req.Payload, 0)
 		res, err := backend.LinkEmailConfirm(ctx, req.UserID, string(in.Email()), string(in.Code()))
 		if err != nil {
 			return nil, err
 		}
-		return encodeLinkResult(res, supportedLangs), nil
+		return encodeLinkResult(res), nil
 	}
 }
 
-func linkEmailMergeHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func linkEmailMergeHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsLinkEmailConfirm(req.Payload, 0)
 		res, err := backend.LinkEmailMerge(ctx, req.UserID, string(in.Email()), string(in.Code()))
 		if err != nil {
 			return nil, err
 		}
-		return encodeLinkResult(res, supportedLangs), nil
+		return encodeLinkResult(res), nil
 	}
 }
 
 // linkTelegramHandler validates Login Widget data via the connector and then calls
 // the backend's link or merge endpoint with the trusted Telegram external id.
-func linkTelegramHandler(backend *backendclient.Client, tg TelegramValidator, merge bool, supportedLangs []string) Handler {
+func linkTelegramHandler(backend *backendclient.Client, tg TelegramValidator, merge bool) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsLinkTelegramRequest(req.Payload, 0)
 		user, err := tg.ValidateLoginWidget(ctx, string(in.Data()))
@@ -84,6 +82,6 @@ func linkTelegramHandler(backend *backendclient.Client, tg TelegramValidator, me
 		if err != nil {
 			return nil, err
 		}
-		return encodeLinkResult(res, supportedLangs), nil
+		return encodeLinkResult(res), nil
 	}
 }

gateway/internal/transcode/transcode_social.go

@@ -246,6 +246,10 @@ func invitationCancelHandler(backend *backendclient.Client) Handler {
 func profileUpdateHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsUpdateProfileRequest(req.Payload, 0)
+		prefs := make([]string, in.VariantPreferencesLength())
+		for i := range prefs {
+			prefs[i] = string(in.VariantPreferences(i))
+		}
 		p := backendclient.ProfileResp{
 			DisplayName:            string(in.DisplayName()),
 			PreferredLanguage:      string(in.PreferredLanguage()),
@@ -255,6 +259,7 @@ func profileUpdateHandler(backend *backendclient.Client) Handler {
 			BlockChat:              in.BlockChat(),
 			BlockFriendRequests:    in.BlockFriendRequests(),
 			NotificationsInAppOnly: in.NotificationsInAppOnly(),
+			VariantPreferences:     prefs,
 		}
 		out, err := backend.UpdateProfile(ctx, req.UserID, p)
 		if err != nil {

gateway/internal/transcode/transcode_telegram_test.go

@@ -43,11 +43,11 @@ func TestTelegramAuthForwardsSeedFields(t *testing.T) {
 			t.Errorf("unexpected path %q", r.URL.Path)
 		}
 		_ = json.NewDecoder(r.Body).Decode(&gotBody)
-		_, _ = w.Write([]byte(`{"token":"tok-tg","user_id":"u-tg","is_guest":false,"display_name":"Иван","service_language":"ru"}`))
+		_, _ = w.Write([]byte(`{"token":"tok-tg","user_id":"u-tg","is_guest":false,"display_name":"Иван"}`))
 	})
 	defer cleanup()
 
-	v := fakeValidator{user: connector.User{ExternalID: "42", Username: "neo", FirstName: "Иван", LanguageCode: "ru", ServiceLanguage: "ru", SupportedLanguages: []string{"ru"}}}
+	v := fakeValidator{user: connector.User{ExternalID: "42", Username: "neo", FirstName: "Иван", LanguageCode: "ru"}}
 	reg := transcode.NewRegistry(backend, v)
 	op, ok := reg.Lookup(transcode.MsgAuthTelegram)
 	if !ok {
@@ -62,48 +62,9 @@ func TestTelegramAuthForwardsSeedFields(t *testing.T) {
 	if string(sess.Token()) != "tok-tg" || string(sess.UserId()) != "u-tg" {
 		t.Fatalf("session decoded wrong: token=%q user=%q", sess.Token(), sess.UserId())
 	}
-	// The validating bot's supported languages ride the Session so the UI gates the
-	// New Game variant choice (here: ru -> Russian + Эрудит only).
-	if got := sessionLanguages(sess); len(got) != 1 || got[0] != "ru" {
-		t.Errorf("session supported_languages = %v, want [ru]", got)
-	}
-	// The bot's service language rides the Session so the UI can build a share link to
-	// the same bot.
-	if got := string(sess.ServiceLanguage()); got != "ru" {
-		t.Errorf("session service_language = %q, want ru", got)
-	}
-	// The validated launch fields are forwarded so the backend can seed a new account;
-	// service_language is recorded to route the account's later out-of-app push.
-	if gotBody["external_id"] != "42" || gotBody["language_code"] != "ru" || gotBody["first_name"] != "Иван" || gotBody["service_language"] != "ru" {
-		t.Errorf("forwarded body = %+v, want external_id=42 language_code=ru first_name=Иван service_language=ru", gotBody)
-	}
-}
-
-// sessionLanguages reads the supported_languages vector off a decoded Session.
-func sessionLanguages(s *fb.Session) []string {
-	out := make([]string, s.SupportedLanguagesLength())
-	for i := range out {
-		out[i] = string(s.SupportedLanguages(i))
-	}
-	return out
-}
-
-// TestGuestAuthSeedsDefaultLanguages confirms a non-platform (guest) session carries
-// the gateway's default supported-languages set, so the web client is ungated.
-func TestGuestAuthSeedsDefaultLanguages(t *testing.T) {
-	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, _ *http.Request) {
-		_, _ = w.Write([]byte(`{"token":"tok-g","user_id":"u-g","is_guest":true,"display_name":"Guest"}`))
-	})
-	defer cleanup()
-
-	reg := transcode.NewRegistry(backend, nil, "en", "ru")
-	op, _ := reg.Lookup(transcode.MsgAuthGuest)
-	payload, err := op.Handler(context.Background(), transcode.Request{})
-	if err != nil {
-		t.Fatalf("handler: %v", err)
-	}
-	if got := sessionLanguages(fb.GetRootAsSession(payload, 0)); len(got) != 2 || got[0] != "en" || got[1] != "ru" {
-		t.Errorf("guest session supported_languages = %v, want [en ru]", got)
+	// The validated launch fields are forwarded so the backend can seed a new account.
+	if gotBody["external_id"] != "42" || gotBody["language_code"] != "ru" || gotBody["first_name"] != "Иван" {
+		t.Errorf("forwarded body = %+v, want external_id=42 language_code=ru first_name=Иван", gotBody)
 	}
 }