fix: UpdateMe 핸들러 내 계층형 메타데이터 처리 및 로그인 ID 동기화 로직 보강

backend/internal/handler/auth_handler.go

@@ -5283,20 +5283,27 @@ func (h *AuthHandler) UpdateMe(c *fiber.Ctx) error {
 	if schemaCompCode != "" && h.TenantService != nil {
 		if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), schemaCompCode); err == nil && tenant != nil {
 			if loginIDField, ok := tenant.Config["loginIdField"].(string); ok && loginIDField != "" {
+				slog.Debug("[UpdateMe] Login ID sync active", "field", loginIDField)
 				// Search in Metadata (could be flat or namespaced)
+				var newLoginID string
 				if val, exists := req.Metadata[loginIDField]; exists {
-					if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
-						traits["id"] = loginIDStr
+					if s, ok := val.(string); ok {
+						newLoginID = s
 					}
 				} else if namespaced, exists := req.Metadata[tenant.ID]; exists {
 					if subMeta, ok := namespaced.(map[string]any); ok {
 						if val, exists := subMeta[loginIDField]; exists {
-							if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
-								traits["id"] = loginIDStr
+							if s, ok := val.(string); ok {
+								newLoginID = s
 							}
 						}
 					}
 				}
+
+				if newLoginID != "" {
+					slog.Info("[UpdateMe] Syncing custom field to LoginID", "field", loginIDField, "value", newLoginID)
+					traits["id"] = newLoginID
+				}
 			}
 		}
 	}