add middleware to check if user is connected

src/Application/Middleware/RequireUserMiddleware.php

+<?php
+declare(strict_types=1);
+
+namespace App\Application\Middleware;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Psr\Http\Server\MiddlewareInterface as Middleware;
+use Psr\Http\Server\RequestHandlerInterface as RequestHandler;
+use Slim\Psr7\Response;
+
+class RequireUserMiddleware implements Middleware
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function process(Request $request, RequestHandler $handler): ResponseInterface
+    {
+        if (isset($request['user'])) {
+            return $handler->handle($request);
+        }
+
+        $response = new Response();
+        return $response->withHeader('Location', '/login')->withStatus(302);
+    }
+}