intent reference generation + propagation

frontend/pshared/lib/api/requests/payment/initiate_payments.dart

@@ -1,13 +1,16 @@
 import 'package:pshared/api/requests/payment/base.dart';
 
-
 class InitiatePaymentsRequest extends PaymentBaseRequest {
   final String quoteRef;
+  final String? intentRef;
+  final List<String>? intentRefs;
 
   const InitiatePaymentsRequest({
     required super.idempotencyKey,
     super.metadata,
     required this.quoteRef,
+    this.intentRef,
+    this.intentRefs,
   });
 
   factory InitiatePaymentsRequest.fromJson(Map<String, dynamic> json) {
@@ -17,6 +20,10 @@ class InitiatePaymentsRequest extends PaymentBaseRequest {
         (key, value) => MapEntry(key, value as String),
       ),
       quoteRef: json['quoteRef'] as String,
+      intentRef: json['intentRef'] as String?,
+      intentRefs: (json['intentRefs'] as List<dynamic>?)
+          ?.map((value) => value as String)
+          .toList(),
     );
   }
 
@@ -26,6 +33,8 @@ class InitiatePaymentsRequest extends PaymentBaseRequest {
       'idempotencyKey': idempotencyKey,
       'metadata': metadata,
       'quoteRef': quoteRef,
+      if (intentRef != null) 'intentRef': intentRef,
+      if (intentRefs != null) 'intentRefs': intentRefs,
     };
   }
 }