chore: code cleanup

src/Exception/AlreadyHoldingResourceException.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exception;
+
+use App\Entity\Booking;
+
+/**
+ * One person may not hold two resources of the same kind at overlapping times. A desk in the
+ * morning and a different one in the afternoon is fine -- only the overlap is refused.
+ */
+final class AlreadyHoldingResourceException extends \RuntimeException
+{
+    public function __construct(public readonly Booking $existing)
+    {
+        $time = $existing->getTimeRange();
+
+        parent::__construct(\sprintf(
+            'Du hast am %s bereits %s gebucht (%s).',
+            $existing->getDate()->format('d.m.Y'),
+            $existing->getResource()->getLabel(),
+            $time,
+        ));
+    }
+}