sendCustomMessage method
发送自定义消息
Implementation
Future<V2TimValueCallback<V2TimMessage>> sendCustomMessage({
required String data,
required String receiver,
required String groupID,
int priority = 0,
String desc = "",
String extension = "",
bool onlineUserOnly = false,
bool isExcludedFromUnreadCount = false,
Map<String, dynamic>? offlinePushInfo,
}) async {
throw UnimplementedError("send() has not been implemented");
}