private function removeOAuthClient($app)
 {
     $client = OAuthClient::find($app->client_id);
     if ($client) {
         $client->delete();
     }
     $endpoint = OAuthClientEndPoint::find($app->client_id);
     if ($endpoint) {
         $endpoint->delete();
     }
     OAuthClientScope::where('client_id', $app->client_id)->delete();
 }