public function getUser()
    {
        if (is_null($this->user)) {
            /**
             * @var \OxidEsales\PayPalModule\Core\Exception\PayPalMissingParameterException $exception
             */
            $exception = oxNew(\OxidEsales\PayPalModule\Core\Exception\PayPalMissingParameterException::class);
            throw $exception;
        }

        return $this->user;
    }