feat: add the booking board with floor plan and calendar

src/Form/BookingRequest.php

@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Form;
+
+use Symfony\Component\Validator\Constraints as Assert;
+
+/**
+ * What the booking modal edits. The resource is fixed by the URL -- only the day is adjustable,
+ * because the modal is opened by clicking a resource on the floor plan.
+ */
+final class BookingRequest
+{
+    public function __construct(
+        #[Assert\NotNull(message: 'Bitte einen Tag wählen.')]
+        #[Assert\GreaterThanOrEqual('today', message: 'Für vergangene Tage kann nicht gebucht werden.')]
+        public ?\DateTimeImmutable $date = null,
+    ) {
+    }
+}