code: protected function sendNotification(FosAvailabilityAlertSubscription $fosAvailabilityAlertSubscription)
      {
          $this->mailHandler->sendAvailabilityAlertMail($fosAvailabilityAlertSubscription);
  
          $fosAvailabilityAlertSubscription->setSentAt(new DateTime())
              ->setStatus(FosAvailabilityAlertSubscriptionTableMap::COL_STATUS_NOTIFIED)
              ->save();
  
          return $this;
      }
docs: @param \Orm\Zed\AvailabilityAlert\Persistence\FosAvailabilityAlertSubscription $fosAvailabilityAlertSubscription
  
  @return \FondOfSpryker\Zed\AvailabilityAlert\Business\Model\SubscribersNotifier