public function extendNotificationChannel()
    {
        if ($this->app->bound(ChannelManager::class)) {
            $channel = $this->app['config']->get('doctrine.notifications.channel', 'database');

            $this->app->make(ChannelManager::class)->extend($channel, function ($app) {
                return new DoctrineChannel($app['registry']);
            });
        }
    }