Fixes the queue for beta 14 (#2363)

- rewrite the queue handling for illuminate 6+
- implement missing maintenance mode callable for queue Worker
- Ensure we resolve append the queue commands once the queue bindings are loaded
- Override WorkCommand because it needs the maintenance flag. It tries to use
the isDownForMaintenance method from the Container assuming it is a Laravel
Application. Circumvented this issue by resolving our Config from IOC instead.

src/Queue/Console/WorkCommand.php

@@ -0,0 +1,27 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Queue\Console;
+
+use Flarum\Foundation\Config;
+
+class WorkCommand extends \Illuminate\Queue\Console\WorkCommand
+{
+    protected function downForMaintenance()
+    {
+        if ($this->option('force')) {
+            return false;
+        }
+
+        /** @var Config $config */
+        $config = $this->laravel->make(Config::class);
+
+        return $config->inMaintenanceMode();
+    }
+}