code: public function run()
      {
          if ($this->checkAccess) {
              call_user_func($this->checkAccess, $this->id);
          }
  
          /* @var $model \yii\db\ActiveRecord */
          $model = new $this->modelClass([
              'scenario' => $this->scenario,
          ]);
  
          $model->load(Yii::$app->getRequest()->getBodyParams(), '');
          if ($model->save()) {
              $response = Yii::$app->getResponse();
              $response->setStatusCode(201);
              $id = implode(',', array_values($model->getPrimaryKey(true)));
              $response->getHeaders()->set('Location', Url::toRoute([$this->viewAction, 'id' => $id], true));
          } elseif (!$model->hasErrors()) {
              throw new ServerErrorHttpException('Failed to create the object for unknown reason.');
          }
  
          return $model;
      }
docs: Creates a new model.
  @return \yii\db\ActiveRecordInterface the model newly created
  @throws ServerErrorHttpException if there is any error when creating the model