Add middleware conforming to the PSR interfaces

app/src/Middleware/VerifyPasswordMiddleware.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Slovocast\Middleware;
+
+use Odan\Session\SessionInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface as RequestHandler;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Psr\Http\Message\ResponseInterface as Response;
+
+class VerifyPasswordMiddleware implements MiddlewareInterface
+{
+    public function __construct(
+        private SessionInterface $session
+    ) {}
+
+    public function process(Request $request, RequestHandler $handler): Response
+    {
+        // get user Data
+        $requestData = $request->getParsedBody();
+
+        if ($requestData['password'] !== $requestData['checked_password']) {
+            
+            $this->session
+                 ->getFlash()
+                 ->add('error', "Passwords do not match.");
+            $response = $handler->handle($request);
+            return $response->withStatus(400);
+        }
+
+        return $handler->handle($request);
+    }
+}