fix: JsonKey for User.language

packages/stream_chat/lib/src/core/models/user.dart

@@ -86,8 +86,7 @@ class User extends Equatable {
   /// The language this user prefers.
   ///
   /// Defaults to 'en'.
-  @JsonKey(
-      includeIfNull: false, toJson: Serializer.readOnly, defaultValue: 'en')
+  @JsonKey(defaultValue: 'en')
   final String? language;
 
   @override

packages/stream_chat/lib/src/core/models/user.g.dart

@@ -48,6 +48,6 @@ Map<String, dynamic> _$UserToJson(User instance) {
   writeNotNull('online', readonly(instance.online));
   writeNotNull('banned', readonly(instance.banned));
   val['extra_data'] = instance.extraData;
-  writeNotNull('language', readonly(instance.language));
+  val['language'] = instance.language;
   return val;
 }