feat(payment): add refund and reversal functionality to payment gateways

- Implemented `refund` and `reverse` methods in `PaymentGatewayInterface`.
- Added `PaymentRefundResult` class to handle refund operation results.
- Enhanced `MockGateway` and `SepGateway` to support refund and reversal operations.
- Updated `PaymentManager` to include `refundPayment` and `reversePayment` methods for handling refunds and reversals in transactions.
- Modified `ClinicSubscriptionRepository` and `SubscriptionService` to manage subscriptions during refunds.
- Added admin API endpoints for processing refunds and reversals.
- Updated security headers to allow form actions to the sandbox environment.
- Documented the new refund and reversal features in the API documentation.

src/Subscription/Repository/ClinicSubscriptionRepository.php

@@ -53,4 +53,15 @@ class ClinicSubscriptionRepository extends ServiceEntityRepository
         $this->getEntityManager()->persist($subscription);
         $this->getEntityManager()->flush();
     }
+
+    public function findByPayment(\App\Payment\Entity\Payment $payment): ?ClinicSubscription
+    {
+        return $this->findOneBy(['payment' => $payment]);
+    }
+
+    public function remove(ClinicSubscription $subscription): void
+    {
+        $this->getEntityManager()->remove($subscription);
+        $this->getEntityManager()->flush();
+    }
 }