Migrated QrCodeCacheMiddleware to psr-15 middleware

module/Core/src/Middleware/QrCodeCacheMiddleware.php

@@ -3,9 +3,11 @@ namespace Shlinkio\Shlink\Core\Middleware;
 
 use Acelaya\ZsmAnnotatedServices\Annotation\Inject;
 use Doctrine\Common\Cache\Cache;
+use Interop\Http\ServerMiddleware\DelegateInterface;
+use Interop\Http\ServerMiddleware\MiddlewareInterface;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
-use Zend\Stratigility\MiddlewareInterface;
+use Zend\Diactoros\Response as DiactResp;
 
 class QrCodeCacheMiddleware implements MiddlewareInterface
 {
@@ -26,44 +28,29 @@ class QrCodeCacheMiddleware implements MiddlewareInterface
     }
 
     /**
-     * Process an incoming request and/or response.
-     *
-     * Accepts a server-side request and a response instance, and does
-     * something with them.
-     *
-     * If the response is not complete and/or further processing would not
-     * interfere with the work done in the middleware, or if the middleware
-     * wants to delegate to another process, it can use the `$out` callable
-     * if present.
-     *
-     * If the middleware does not return a value, execution of the current
-     * request is considered complete, and the response instance provided will
-     * be considered the response to return.
-     *
-     * Alternately, the middleware may return a response instance.
-     *
-     * Often, middleware will `return $out();`, with the assumption that a
-     * later middleware will return a response.
+     * Process an incoming server request and return a response, optionally delegating
+     * to the next middleware component to create the response.
      *
      * @param Request $request
-     * @param Response $response
-     * @param null|callable $out
-     * @return null|Response
+     * @param DelegateInterface $delegate
+     *
+     * @return Response
      */
-    public function __invoke(Request $request, Response $response, callable $out = null)
+    public function process(Request $request, DelegateInterface $delegate)
     {
         $cacheKey = $request->getUri()->getPath();
 
         // If this QR code is already cached, just return it
         if ($this->cache->contains($cacheKey)) {
             $qrData = $this->cache->fetch($cacheKey);
+            $response = new DiactResp();
             $response->getBody()->write($qrData['body']);
             return $response->withHeader('Content-Type', $qrData['content-type']);
         }
 
         // If not, call the next middleware and cache it
         /** @var Response $resp */
-        $resp = $out($request, $response);
+        $resp = $delegate->process($request);
         $this->cache->save($cacheKey, [
             'body' => $resp->getBody()->__toString(),
             'content-type' => $resp->getHeaderLine('Content-Type'),