Expand config API endpoint.

app/Support/Binder/ConfigurationName.php

@@ -0,0 +1,51 @@
+<?php
+/**
+ * ConfigurationName.php
+ * Copyright (c) 2018 thegrumpydictator@gmail.com
+ *
+ * This file is part of Firefly III.
+ *
+ * Firefly III is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Firefly III is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Firefly III. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace FireflyIII\Support\Binder;
+
+
+use Illuminate\Routing\Route;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+
+/**
+ * Class ConfigurationName
+ */
+class ConfigurationName implements BinderInterface
+{
+
+    /**
+     * @param string $value
+     * @param Route  $route
+     *
+     * @return string
+     * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
+     */
+    public static function routeBinder(string $value, Route $route): string
+    {
+        $accepted = ['is_demo_site', 'permission_update_check', 'single_user_mode'];
+        if (\in_array($value, $accepted, true)) {
+            return $value;
+        }
+        throw new NotFoundHttpException;
+    }
+}