feat(demo): add story 1 — Sorano: Rock and Time

plugins/email/vendor/symfony/messenger/Middleware/StackInterface.php

@@ -0,0 +1,25 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Messenger\Middleware;
+
+/**
+ * @author Nicolas Grekas <p@tchwork.com>
+ *
+ * Implementations must be cloneable, and each clone must unstack the stack independently.
+ */
+interface StackInterface
+{
+    /**
+     * Returns the next middleware to process a message.
+     */
+    public function next(): MiddlewareInterface;
+}