/**
  * Delete channel
  */
 public function actionDelete($id)
 {
     $channelId = new \MongoId($id);
     $articleCount = Article::countByChannel($channelId);
     if ($articleCount > 0) {
         return $articleCount;
     }
     if (!ArticleChannel::deleteAll(['_id' => $channelId])) {
         throw new ServerErrorHttpException("failed to delete article channel for unknown reason");
     }
     Yii::$app->getResponse()->setStatusCode(204);
 }