feat: mail service

integration/internal/harness/mail_stub.go

@@ -22,6 +22,9 @@ type LoginCodeDelivery struct {
 
 	// Code stores the cleartext login code requested by authsession.
 	Code string
+
+	// Locale stores the canonical BCP 47 language tag selected by authsession.
+	Locale string
 }
 
 // MailBehavior overrides one external mail-stub response.
@@ -100,8 +103,9 @@ func (s *MailStub) handle(writer http.ResponseWriter, request *http.Request) {
 	}
 
 	var payload struct {
-		Email string `json:"email"`
-		Code  string `json:"code"`
+		Email  string `json:"email"`
+		Code   string `json:"code"`
+		Locale string `json:"locale"`
 	}
 	if err := decodeStrictJSONRequest(request, &payload); err != nil {
 		http.Error(writer, err.Error(), http.StatusBadRequest)
@@ -110,8 +114,9 @@ func (s *MailStub) handle(writer http.ResponseWriter, request *http.Request) {
 
 	s.mu.Lock()
 	s.deliveries = append(s.deliveries, LoginCodeDelivery{
-		Email: payload.Email,
-		Code:  payload.Code,
+		Email:  payload.Email,
+		Code:   payload.Code,
+		Locale: payload.Locale,
 	})
 	behavior := s.behavior
 	s.mu.Unlock()