Add example chat.php redirect script

Author: themightychris

site-root/chat.php

@@ -0,0 +1,13 @@
+<?php
+
+// TODO: delete/comment this line and use this file to implement a gateway to your group's chat system
+return RequestHandler::throwError('The administrator of this site has not yet implemented a redirect to your chat provider');
+
+// $_GET['channel'] may be provided to indicate a specific channel to redirect to
+
+// EXAMPLE 1: Redirect to Slack with authentication provided via SAML Single Sign On
+//$GLOBALS['Session']->requireAuthentication();
+//Site::redirect('https://codeforphilly.slack.com/sso/saml/start?redir=%2Fmessages%2F'.urlencode(!empty($_GET['channel']) ? $_GET['channel'] : 'general').'%2F');
+
+// EXAMPLE 2: Redirect to Slack without SSO
+//Site::redirect('https://codeforphilly.slack.com/messages/'.urlencode(!empty($_GET['channel']) ? $_GET['channel'] : 'general').'/');