small fixes for single payout and big chunck for multiple payouts

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

@@ -0,0 +1,31 @@
+import 'package:pshared/api/requests/payment/base.dart';
+
+
+class InitiatePaymentsRequest extends PaymentBaseRequest {
+  final String quoteRef;
+
+  const InitiatePaymentsRequest({
+    required super.idempotencyKey,
+    super.metadata,
+    required this.quoteRef,
+  });
+
+  factory InitiatePaymentsRequest.fromJson(Map<String, dynamic> json) {
+    return InitiatePaymentsRequest(
+      idempotencyKey: json['idempotencyKey'] as String,
+      metadata: (json['metadata'] as Map<String, dynamic>?)?.map(
+        (key, value) => MapEntry(key, value as String),
+      ),
+      quoteRef: json['quoteRef'] as String,
+    );
+  }
+
+  @override
+  Map<String, dynamic> toJson() {
+    return <String, dynamic>{
+      'idempotencyKey': idempotencyKey,
+      'metadata': metadata,
+      'quoteRef': quoteRef,
+    };
+  }
+}