completed group batch feature

lib/screens/gateway/gateway_controller.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:qpay/http/http.dart';
 import 'package:qpay/models/api_response.dart';
 import 'package:qpay/screens/transaction_controller.dart';
+import 'package:qpay/widgets/app_snack_bar.dart';
 import 'package:provider/provider.dart';
 
 class GatewayModel {
@@ -30,13 +31,7 @@ class GatewayController extends ChangeNotifier {
 
   void _showErrorSnackBar(String? message) {
     WidgetsBinding.instance.addPostFrameCallback((_) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(
-          content: Text(message.toString()),
-          behavior: SnackBarBehavior.floating,
-          backgroundColor: Colors.deepOrange,
-        ),
-      );
+      AppSnackBar.showError(context, message.toString());
     });
   }