Mail Extender (#2012)

This allows registering new drivers, or overwriting existing ones.

framework/core/src/Extend/Mail.php

@@ -0,0 +1,38 @@
+<?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\Extend;
+
+use Flarum\Extension\Extension;
+use Illuminate\Contracts\Container\Container;
+
+class Mail implements ExtenderInterface
+{
+    protected $drivers = [];
+
+    /**
+     * Add a mail driver.
+     *
+     * @param string $identifier Identifier for mail driver. E.g. 'smtp' for SmtpDriver
+     * @param string $driver ::class attribute of driver class, which must implement Flarum\Mail\DriverInterface
+     */
+    public function driver(string $identifier, $driver)
+    {
+        $this->drivers[$identifier] = $driver;
+
+        return $this;
+    }
+
+    public function extend(Container $container, Extension $extension = null)
+    {
+        $container->extend('mail.supported_drivers', function ($existingDrivers) {
+            return array_merge($existingDrivers, $this->drivers);
+        });
+    }
+}