[Web] Do not allow to add domain admin for non existing domain

[Web] oAuth2 implementation (wip)

data/web/oauth/token.php

@@ -0,0 +1,4 @@
+<?php
+require_once $_SERVER['DOCUMENT_ROOT'] . '/inc/prerequisites.inc.php';
+$request = OAuth2\Request::createFromGlobals();
+$oauth2_server->handleTokenRequest($request)->send();