feat: add the product code to the travel export

src/Service/TravelExportBuilder.php

@@ -157,9 +157,14 @@ class TravelExportBuilder
             $pickupsWithoutMasterData,
         );
 
+        // The product a date belongs to, from the enclosing <reise>. Not derivable from the
+        // date code: DWWMP runs dates coded DWWMW…, and group travels carry each group's code.
+        $productNode = $node->getNode(0)?->parentNode;
+
         $travel = [
             'busProId' => $travelId,
             'code' => $node->attr('code'),
+            'productCode' => $productNode instanceof \DOMElement ? $this->trimOrNull($productNode->getAttribute('code')) : null,
             'product' => $this->trimOrNull($this->getStringOrNullValue($node->filterXPath('.//text'))),
             'dateFrom' => $dateFrom->format('Y-m-d'),
             'dateTo' => $dateTo->format('Y-m-d'),