feat(demo): add story 1 — Sorano: Rock and Time

plugins/api/classes/Api/Exceptions/ForbiddenException.php

@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Grav\Plugin\Api\Exceptions;
+
+class ForbiddenException extends ApiException
+{
+    public function __construct(string $detail = 'You do not have permission to perform this action.', ?\Throwable $previous = null)
+    {
+        parent::__construct(403, 'Forbidden', $detail, [], $previous);
+    }
+}