Add SecurePay callback URL

Author: amacneil

src/Omnipay/SecurePay/Message/DirectPostAuthorizeRequest.php

@@ -31,6 +31,8 @@ public function getData()
         $data['EPS_TIMESTAMP'] = gmdate('YmdHis');
         $data['EPS_FINGERPRINT'] = $this->generateFingerprint($data);
         $data['EPS_RESULTURL'] = $this->getReturnUrl();
+        $data['EPS_CALLBACKURL'] = $this->getReturnUrl();
+        $data['EPS_REDIRECT'] = 'TRUE';
         $data['EPS_CURRENCY'] = $this->getCurrency();
 
         return $data;