Add "clear cache" button to admin

src/Api/Controller/ClearCacheController.php

@@ -0,0 +1,56 @@
+<?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\Api\Controller;
+
+use Flarum\Foundation\Application;
+use Flarum\Foundation\Console\CacheClearCommand;
+use Flarum\Settings\SettingsRepositoryInterface;
+use Flarum\User\AssertPermissionTrait;
+use League\Flysystem\Adapter\Local;
+use League\Flysystem\Filesystem;
+use Psr\Http\Message\ServerRequestInterface;
+use Symfony\Component\Console\Input\ArrayInput;
+use Symfony\Component\Console\Output\NullOutput;
+use Zend\Diactoros\Response\EmptyResponse;
+
+class ClearCacheController extends AbstractDeleteController
+{
+    use AssertPermissionTrait;
+
+    /**
+     * @var CacheClearCommand
+     */
+    protected $command;
+
+    /**
+     * @param CacheClearCommand $command
+     */
+    public function __construct(CacheClearCommand $command)
+    {
+        $this->command = $command;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function delete(ServerRequestInterface $request)
+    {
+        $this->assertAdmin($request->getAttribute('actor'));
+
+        $this->command->run(
+            new ArrayInput([]),
+            new NullOutput()
+        );
+
+        return new EmptyResponse(204);
+    }
+}