logout method
Implementation
Future<void> logout() async {
final credentials = _credentials;
if (credentials == null) {
return;
}
_credentials = null;
await _clearCredentials();
try {
await http.post(
logoutEndpoint,
headers: {'Content-Type': 'application/x-www-form-urlencoded'},
body: {
'client_id': clientId,
'refresh_token': credentials.refreshToken,
},
);
} catch (_) {}
}