feat: implement idempotency key for critical API endpoints

lib/domain/order/repositories/i_order_repository.dart

@@ -24,10 +24,12 @@ abstract class IOrderRepository {
   Future<Either<OrderFailure, Order>> addItemOrder({
     required String id,
     required List<AddItemOrderRequest> request,
+    String? idempotencyKey,
   });
 
   Future<Either<OrderFailure, Payment>> createPayment({
     required PaymentRequest request,
+    String? idempotencyKey,
   });
 
   Future<Either<OrderFailure, Unit>> voidOrder({
@@ -35,15 +37,18 @@ abstract class IOrderRepository {
     required String reason,
     String type = "ITEM", // TYPE: ALL, ITEM
     required List<OrderItem> orderItems,
+    String? idempotencyKey,
   });
 
   Future<Either<OrderFailure, Payment>> createSplitBill(
-    PaymentSplitBillRequest request,
-  );
+    PaymentSplitBillRequest request, {
+    String? idempotencyKey,
+  });
 
   Future<Either<OrderFailure, Unit>> refundOrder({
     required String id,
     required String reason,
     required int refundAmount,
+    String? idempotencyKey,
   });
 }