feat: voucher purchase flow

src/BusProNet/Model/VoucherPaymentMethod.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\BusProNet\Model;
+
+/**
+ * A payment method for voucher purchases (GUTSCHEINZAHLUNGSARTEN).
+ *
+ * Echoed unchanged as the <zahlung> attributes of GUTSCHEINBUCHUNG.
+ */
+final readonly class VoucherPaymentMethod
+{
+    public const string TYPE_TRANSFER = 'UEBERW';
+
+    public function __construct(
+        public int $id,
+        public string $label,
+        public string $type,
+    ) {
+    }
+
+    public function isTransfer(): bool
+    {
+        return self::TYPE_TRANSFER === $this->type;
+    }
+}