[BUGFIX] Do not boot Slim if route prefix not exactly matched

If the route prefix is `/api`, Slim must not boot for an url like `/api-external`.

In order to fix that, the route prefix is know matched like `/api/`.

The only downside is that `/api` (without trailing slash) is not handled by Slim anymore.

Author: dogawaf

src/Middleware/SlimInitiator.php

@@ -62,7 +62,7 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
                 continue;
             }
 
-            $prefix = $config['route'] ?? '/';
+            $prefix = rtrim($config['route'], '/') . '/';
             if (strpos($request->getUri()->getPath(), $prefix) !== 0) {
                 continue;
             }