Add flood control

closes #271

src/Core/Exception/FloodingException.php

@@ -0,0 +1,33 @@
+<?php
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Core\Exception;
+
+use Exception;
+use Tobscure\JsonApi\Exception\JsonApiSerializableInterface;
+
+class FloodingException extends Exception implements JsonApiSerializableInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getStatusCode()
+    {
+        return 429;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getErrors()
+    {
+        return [];
+    }
+}