setUserId method
Set a user ID.
important : When the setUserId API is called, if the old userId is not
empty and is different from the new userId, a new session is generated.
If you do not want to use setUserId to identify a user
(for example, when a user signs out), set userId to null.
The SDK does not save the user ID. You are advised to set a user ID each time after the app is launched.
Implementation
Future<void> setUserId(String? userId) async {
await _channel.invokeMethod('setUserId', {'userId': userId});
}