public function addPaymentTransaction(PaymentTransaction $paymentTransaction)
    {
        if (!$this->hasPaymentTransaction($paymentTransaction))
        {
            $this->paymentTransactions[] = $paymentTransaction;
        }

        if ($paymentTransaction->getPayment() !== $this)
        {
            $paymentTransaction->setPayment($this);
        }

        return $this;
    }