added optional powered-by header (#2618)

framework/core/src/Http/Middleware/FlarumPromotionHeader.php

@@ -0,0 +1,37 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Http\Middleware;
+
+use Flarum\Foundation\Config;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface as Middleware;
+use Psr\Http\Server\RequestHandlerInterface;
+
+class FlarumPromotionHeader implements Middleware
+{
+    protected $enabled = true;
+
+    public function __construct(Config $config)
+    {
+        $this->enabled = $config['poweredByHeader'] ?? true;
+    }
+
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        $response = $handler->handle($request);
+
+        if ($this->enabled) {
+            $response = $response->withAddedHeader('X-Powered-By', 'Flarum');
+        }
+
+        return $response;
+    }
+}