Queue support (#1773)

Implementation of clean queue handling, by default sync is used

src/Queue/QueueFactory.php

@@ -0,0 +1,57 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Queue;
+
+use Illuminate\Contracts\Queue\Factory;
+
+class QueueFactory implements Factory
+{
+    /**
+     * @var callable
+     */
+    private $factory;
+
+    /**
+     * The cached queue instance.
+     *
+     * @var \Illuminate\Contracts\Queue\Queue
+     */
+    private $queue;
+
+    /**
+     * QueueFactory constructor.
+     *
+     * Expects a callback that will be called to instantiate the queue adapter,
+     * once requested by the application.
+     *
+     * @param callable $factory
+     */
+    public function __construct(callable $factory)
+    {
+        $this->factory = $factory;
+    }
+
+    /**
+     * Resolve a queue connection instance.
+     *
+     * @param string $name
+     * @return \Illuminate\Contracts\Queue\Queue
+     */
+    public function connection($name = null)
+    {
+        if (is_null($this->queue)) {
+            $this->queue = ($this->factory)();
+        }
+
+        return $this->queue;
+    }
+}