accept null value for requests.

Author: Reza-deriv

lib/basic_api/request.dart

@@ -7,6 +7,7 @@ class Request extends Equatable {
     this.msgType,
     this.passthrough,
     this.reqId,
+    this.acceptNullValue = false,
   });
 
   /// Generate an instance from JSON.
@@ -25,6 +26,9 @@ class Request extends Equatable {
   /// [Optional] Used to map request to response.
   final int? reqId;
 
+  /// Determine accept null value in request or not.
+  final bool acceptNullValue;
+
   /// Converts an instance to JSON.
   Map<String, dynamic> toJson() => <String, dynamic>{
         'passthrough': passthrough,

lib/services/connection/call_manager/base_call_manager.dart

@@ -105,8 +105,13 @@ abstract class BaseCallManager<T> {
     required Request request,
     required bool isSubscription,
   }) {
-    final Map<String, dynamic> result = request.toJson()
-      ..removeWhere((String key, dynamic value) => value == null);
+    final Map<String, dynamic> result;
+    if (request.acceptNullValue) {
+      result = request.toJson();
+    } else {
+      result = request.toJson()
+        ..removeWhere((String key, dynamic value) => value == null);
+    }
 
     if (isSubscription) {
       result.putIfAbsent('subscribe', () => 1);