public void IssueBankCard(int accountId)
        {
            if (Closed)
            {
                throw new ValidationException("The account is closed");
            }

            if (BankCards.Any(card => card.AccountId == accountId && !card.Disabled))
            {
                throw new ValidationException("An account may only have one active bank card at a time.");
            }

            BankCards.Add(new BankCard(Id));
        }