updated document upload according to fresh api

frontend/pshared/lib/data/dto/payment/operation.dart

@@ -1,6 +1,7 @@
 class PaymentOperationDTO {
   final String? stepRef;
   final String? operationRef;
+  final String? gateway;
   final String? code;
   final String? state;
   final String? label;
@@ -12,6 +13,7 @@ class PaymentOperationDTO {
   const PaymentOperationDTO({
     this.stepRef,
     this.operationRef,
+    this.gateway,
     this.code,
     this.state,
     this.label,
@@ -25,6 +27,7 @@ class PaymentOperationDTO {
       PaymentOperationDTO(
         stepRef: _asString(json['stepRef'] ?? json['step_ref']),
         operationRef: _asString(json['operationRef'] ?? json['operation_ref']),
+        gateway: _asString(json['gateway']),
         code: _asString(json['code']),
         state: _asString(json['state']),
         label: _asString(json['label']),
@@ -39,6 +42,7 @@ class PaymentOperationDTO {
   Map<String, dynamic> toJson() => <String, dynamic>{
     'stepRef': stepRef,
     'operationRef': operationRef,
+    'gateway': gateway,
     'code': code,
     'state': state,
     'label': label,

frontend/pshared/lib/data/mapper/payment/operation.dart

@@ -1,11 +1,11 @@
 import 'package:pshared/data/dto/payment/operation.dart';
 import 'package:pshared/models/payment/execution_operation.dart';
 
-
 extension PaymentOperationDTOMapper on PaymentOperationDTO {
   PaymentExecutionOperation toDomain() => PaymentExecutionOperation(
     stepRef: stepRef,
     operationRef: operationRef,
+    gateway: gateway,
     code: code,
     state: state,
     label: label,
@@ -20,6 +20,7 @@ extension PaymentExecutionOperationMapper on PaymentExecutionOperation {
   PaymentOperationDTO toDTO() => PaymentOperationDTO(
     stepRef: stepRef,
     operationRef: operationRef,
+    gateway: gateway,
     code: code,
     state: state,
     label: label,