[Api] Check Notify (always return json) (#10059)

* BEAKING: check return status based on struct not httpStatus

* update Tests

* CI.restart()

templates/swagger/v1_json.tmpl

@@ -530,9 +530,6 @@
         "responses": {
           "200": {
             "$ref": "#/responses/NotificationCount"
-          },
-          "204": {
-            "description": "No unread notification"
           }
         }
       }