feat: implement idempotency key for critical API endpoints

lib/infrastructure/order/datasources/remote_data_provider.dart

@@ -18,6 +18,15 @@ class OrderRemoteDataProvider {
   final _logName = 'OrderRemoteDataProvider';
   OrderRemoteDataProvider(this._apiClient);
 
+  /// Helper untuk merge auth header dengan idempotency key
+  Map<String, dynamic> _buildHeaders({String? idempotencyKey}) {
+    final headers = getAuthorizationHeader();
+    if (idempotencyKey != null) {
+      headers['X-Idempotency-Key'] = idempotencyKey;
+    }
+    return headers;
+  }
+
   Future<DC<OrderFailure, ListOrderDto>> fetchOrders({
     int page = 1,
     int limit = 10,
@@ -151,13 +160,14 @@ class OrderRemoteDataProvider {
   }
 
   Future<DC<OrderFailure, PaymentDto>> storePayment(
-    PaymentRequestDto request,
-  ) async {
+    PaymentRequestDto request, {
+    String? idempotencyKey,
+  }) async {
     try {
       final response = await _apiClient.post(
         ApiPath.payments,
         data: request.toJson(),
-        headers: getAuthorizationHeader(),
+        headers: _buildHeaders(idempotencyKey: idempotencyKey),
       );
 
       if (response.data['success'] == false) {
@@ -178,6 +188,7 @@ class OrderRemoteDataProvider {
   Future<DC<OrderFailure, OrderDto>> addItemOrder({
     required String id,
     required List<AddItemOrderRequestDto> request,
+    String? idempotencyKey,
   }) async {
     try {
       final response = await _apiClient.post(
@@ -186,7 +197,7 @@ class OrderRemoteDataProvider {
           'notes': '',
           'order_items': request.map((e) => e.toRequest()).toList(),
         },
-        headers: getAuthorizationHeader(),
+        headers: _buildHeaders(idempotencyKey: idempotencyKey),
       );
 
       if (response.data['success'] == false) {
@@ -209,6 +220,7 @@ class OrderRemoteDataProvider {
     required String reason,
     String type = "ITEM", // TYPE: ALL, ITEM
     required List<OrderItemDto> orderItems,
+    String? idempotencyKey,
   }) async {
     try {
       final response = await _apiClient.post(
@@ -223,7 +235,7 @@ class OrderRemoteDataProvider {
               )
               .toList(),
         },
-        headers: getAuthorizationHeader(),
+        headers: _buildHeaders(idempotencyKey: idempotencyKey),
       );
 
       if (response.data['success'] == false) {
@@ -238,14 +250,15 @@ class OrderRemoteDataProvider {
   }
 
   Future<DC<OrderFailure, PaymentDto>> createSplitBill(
-    PaymentSplitBillRequestDto request,
-  ) async {
+    PaymentSplitBillRequestDto request, {
+    String? idempotencyKey,
+  }) async {
     log(request.toRequest().toString());
     try {
       final response = await _apiClient.post(
         "${ApiPath.orders}/split-bill",
         data: request.toRequest(),
-        headers: getAuthorizationHeader(),
+        headers: _buildHeaders(idempotencyKey: idempotencyKey),
       );
 
       if (response.data['success'] == false) {
@@ -267,12 +280,13 @@ class OrderRemoteDataProvider {
     required String id,
     required String reason,
     required int refundAmount,
+    String? idempotencyKey,
   }) async {
     try {
       final response = await _apiClient.post(
         '${ApiPath.orders}/$id/refund',
         data: {'refund_amount': refundAmount, 'reason': reason},
-        headers: getAuthorizationHeader(),
+        headers: _buildHeaders(idempotencyKey: idempotencyKey),
       );
 
       if (response.data['success'] == false) {