Initial MailGateway module structure

Api/Admin.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Box\Mod\Mailgateway\Api;
+
+class Admin extends \FOSSBilling\Api\AbstractApi
+{
+    public function ping(array $data): array
+    {
+        return [
+            'status' => 'ok',
+            'module' => 'mailgateway',
+            'version' => '0.1.0',
+        ];
+    }
+}