S3/Minio storage controller Support

storage-controllers/s3/GuzzleHttp/Promise/functions_include.php

@@ -0,0 +1,6 @@
+<?php
+
+// Don't redefine the functions if included multiple times.
+if (!function_exists('GuzzleHttp\Promise\promise_for')) {
+    require __DIR__ . '/functions.php';
+}