isValid method
Checks to see if the session is still valid based on session expiry information found in tokens and the current time (adjusted with clock drift)
Implementation
bool isValid() {
if (_invalidated) {
return false;
}
final now = (DateTime.now().millisecondsSinceEpoch / 1000).floor();
final adjusted = now - clockDrift!;
return adjusted < accessToken.getExpiration() &&
adjusted < idToken.getExpiration();
}