isExpired method Null safety
- EngineNotification notification
 
Check if a notification is expired based on valid age and creation time
Implementation
bool isExpired(EngineNotification notification) {
  if (notification.createdUtc.isEmpty ||
      notification.validAge == Duration.zero) {
    return false;
  }
  try {
    final createdAt = DateTime.parse(notification.createdUtc);
    return DateTime.now().isAfter(createdAt.add(notification.validAge));
  } on Error {
    return false;
  }
}