public PaymentNotification(Account account, Transaction transaction, PaymentNotificationType type)
     : base(account)
 {
     PaymentNotificationType = type;
     Transaction = transaction;
 }
 public PaymentNotification(XDocument document, PaymentNotificationType type)
     : base(document)
 {
     PaymentNotificationType = type;
     Transaction = new Transaction(document);
 }