feat: backend service

backend/internal/user/errors.go

@@ -0,0 +1,27 @@
+package user
+
+import "errors"
+
+// ErrAccountNotFound is returned by lookups against `backend.accounts`
+// when the row is missing or has been soft-deleted. Handlers map it to
+// HTTP 404.
+var ErrAccountNotFound = errors.New("user: account not found")
+
+// ErrInvalidInput marks a request as syntactically valid but
+// semantically rejected (empty display name when the field was
+// supplied, blank time zone, etc.). Handlers map it to HTTP 400.
+var ErrInvalidInput = errors.New("user: invalid input")
+
+// ErrInvalidTier is returned by ApplyEntitlement when the supplied tier
+// does not belong to the closed MVP set documented in
+// `backend/README.md`. Handlers map it to HTTP 400.
+var ErrInvalidTier = errors.New("user: invalid tier")
+
+// ErrInvalidSanctionCode marks an ApplySanction request whose
+// sanction_code is not in the closed MVP set ({permanent_block}).
+var ErrInvalidSanctionCode = errors.New("user: invalid sanction code")
+
+// ErrInvalidActor is returned when an admin-side mutation arrives
+// without a non-empty actor.type. The user-side mutations populate
+// actor.type internally and never produce this error.
+var ErrInvalidActor = errors.New("user: invalid actor")