auth method

Implementation

@override
Future<AuthUser?> auth() async {
  if (twilioLoginNode == null) throw 'Login Node is required for authentication';
  Map? result = await _fly.mutation([twilioLoginNode!],
      parsers: {twilioLoginNode!.name: AuthProviderUser()});
  AuthProviderUser user = result?[twilioLoginNode!.name];
  return user;
}