feat: voucher purchase flow

src/Model/PurchaseFlow.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Model;
+
+/**
+ * The purchase flows that start on the login page (optional sign-in, or continue as a guest).
+ */
+enum PurchaseFlow: string
+{
+    case Booking = 'booking';
+    case Voucher = 'voucher';
+
+    public function firstStepRoute(): string
+    {
+        return match ($this) {
+            self::Booking => 'app_booking_create_step_1',
+            self::Voucher => 'app_voucher_step_1',
+        };
+    }
+
+    public function authenticateTemplate(): string
+    {
+        return match ($this) {
+            self::Booking => 'booking/create/authenticate.html.twig',
+            self::Voucher => 'voucher/authenticate.html.twig',
+        };
+    }
+}