code: public function isAlreadySubscribed(
          AvailabilityAlertSubscriptionTransfer $availabilityAlertSubscriptionTransfer
      ) {
          $availabilityAlertSubscriptionTransfer->requireEmail();
          $availabilityAlertSubscriptionTransfer->requireFkProductAbstract();
  
          $subscriptionCount = $this->queryContainer
              ->querySubscriptionByEmailAndIdProductAbstractAndStatus(
                  $availabilityAlertSubscriptionTransfer->getEmail(),
                  $availabilityAlertSubscriptionTransfer->getFkProductAbstract(),
                  FosAvailabilityAlertSubscriptionTableMap::COL_STATUS_PENDING
              )->count();
  
          return $subscriptionCount === 1;
      }
docs: @param \Generated\Shared\Transfer\AvailabilityAlertSubscriptionTransfer $availabilityAlertSubscriptionTransfer
  
  @return bool