code: public function processAvailabilityAlertSubscription(
          AvailabilityAlertSubscriptionTransfer $availabilityAlertSubscriptionTransfer
      ) {
          $subscriptionResponse = $this->createSubscriptionResponse();
  
          $subscriptionResponse->setIsSuccess(true);
  
          try {
              if (!$this->subscriptionManager->isAlreadySubscribed($availabilityAlertSubscriptionTransfer)) {
                  $this->subscriptionManager->subscribe($availabilityAlertSubscriptionTransfer);
              }
          } catch (Exception $e) {
              $subscriptionError = $this->createSubscriptionError();
  
              $subscriptionError->setMessage($e->getMessage());
  
              $subscriptionResponse->setIsSuccess(false)
                  ->addError($subscriptionError);
          }
  
          return $subscriptionResponse;
      }
docs: @param \Generated\Shared\Transfer\AvailabilityAlertSubscriptionTransfer $availabilityAlertSubscriptionTransfer
  
  @return \Generated\Shared\Transfer\AvailabilityAlertSubscriptionResponseTransfer