refactor: implement middleware chain (#4240)

* refactor: implement middleware chain

* refactor

middlewares/SecurityMiddleware.php

@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Make sure that only strings are allowed in GET parameters
+ */
+class SecurityMiddleware implements Middleware
+{
+    public function __invoke(Request $request, $next): Response
+    {
+        foreach ($request->toArray() as $key => $value) {
+            if (!is_string($value)) {
+                return new Response(render(__DIR__ . '/../templates/error.html.php', [
+                    'message' => "Query parameter \"$key\" is not a string.",
+                ]), 400);
+            }
+        }
+        return $next($request);
+    }
+}