fix: don't submit data of removed fields

src/BusProNet/Constants.php

@@ -47,4 +47,8 @@ final class Constants
     public const STATUS_AVAILABLE = 'Frei';
     public const STATUS_BLOCKED = 'Buchungsstop';
     public const STATUS_ON_REQUEST = 'Anfrage';
+
+    // Payment methods
+    public const PAYMENT_METHOD_TRANSFER = 'transfer';
+    public const PAYMENT_METHOD_DEBIT = 'debit';
 }