feat: fetch additional content from cms via api

src/BusProNet/Model/Travel.php

@@ -26,6 +26,9 @@ class Travel
     #[Groups(['api:list', 'api:single'])]
     public ?string $code = null;
 
+    #[Groups(['api:list', 'api:single'])]
+    public ?string $productCode = null;
+
     #[Groups(['api:list', 'api:single'])]
     public ?string $label = null;