isValid method
Implementation
bool isValid() {
if (expiresAt.isEmpty || expiresAt == 'no token') return false;
bool timeValid = Clock.now().isBefore(
DateTime.fromMillisecondsSinceEpoch(int.parse(expiresAt) * 1000));
bool tokenExist = accessToken.isNotEmpty && accessToken != 'no token';
return timeValid && tokenExist;
}