UpdateMessageContent.fromJson constructor
Parse from a json
Implementation
factory UpdateMessageContent.fromJson(Map<String, dynamic> json) => UpdateMessageContent(
  chatId: json['chat_id'],
  messageId: json['message_id'],
  newContent: MessageContent.fromJson(json['new_content']),
  extra: json['@extra'],
  clientId: json['@client_id'],
);