sendGroupMessage method
Implementation
@override
Future<String?> sendGroupMessage(String topic, dynamic message,
String authorityId, String typeId, int versionMajor) async {
await _ensureInitialized();
final contentBytes = _extractContentBytes(message, authorityId, typeId,
versionMajor);
return rust_messaging.sendGroupMessage(
topic: topic, contentBytes: contentBytes);
}