refactor: consider text article in vat calc

src/QUI/ERP/Coupons/CouponCode.php

@@ -559,6 +559,13 @@ public function addToOrder(QUI\ERP\Order\OrderInProcess $Order)
 
         $priceFactors = [];
         $articles     = [];
+        $calculations = $Order->getArticles()->getCalculations();
+        $vatArray     = $calculations['vatArray'];
+        $vat          = false;
+
+        if (\count($vatArray) === 1) {
+            $vat = \array_key_first($vatArray);
+        }
 
         foreach ($coupons as $coupon) {
             /* @var $Coupon CouponCode */
@@ -578,6 +585,11 @@ public function addToOrder(QUI\ERP\Order\OrderInProcess $Order)
 
             foreach ($discounts as $Discount) {
                 $PriceFactor = $Discount->toPriceFactor();
+
+                if ($vat !== false) {
+                    $PriceFactor->setVat($vat);
+                }
+
                 $PriceFactor->setTitle(
                     QUI::getLocale()->get('quiqqer/coupons', 'coupon.discount.title', [
                         'code' => $Coupon->getCode()