public function subscribe(UserInterface $user, PlanInterface $plan)
 {
     $subscription = new $this->class();
     $subscription->setName($plan->getName())->setCurrency($plan->getCurrency())->setPrice($plan->getPrice())->setDiscount($plan->getDiscount())->setPlan($plan);
     $user->addSubscription($subscription);
     $this->event_dispatcher->dispatch(SaaSEvents::SUBSCRIBED, new SubscriptionEvent($subscription));
     return $subscription;
 }