fix: port mailbox validation from im server

internal/httpapi/response.go

@@ -17,6 +17,7 @@ const (
 	reasonForbidden        = "FORBIDDEN"
 	reasonNotFound         = "RESOURCE_NOT_FOUND"
 	reasonConflict         = "CONFLICT"
+	reasonValidationFailed = "VALIDATION_FAILED"
 	reasonInternal         = "INTERNAL"
 )
 
@@ -57,6 +58,8 @@ func writeStoreError(w http.ResponseWriter, r *http.Request, err error) {
 		writeError(w, r, http.StatusForbidden, 30041, reasonForbidden, "forbidden", nil)
 	case errors.Is(err, ErrConflict), errors.Is(err, store.ErrConflict):
 		writeError(w, r, http.StatusConflict, 30040, reasonConflict, "conflict", nil)
+	case errors.Is(err, store.ErrPolicy):
+		writeError(w, r, http.StatusBadRequest, 30000, reasonValidationFailed, "validation failed", nil)
 	default:
 		writeError(w, r, http.StatusInternalServerError, 90000, reasonInternal, "internal error", nil)
 	}