Setting Pancake up to use your own server for oAuth 2 authentication is simple. Find the following file:
system/pancake/config/oauth2_gmail.php
http://path.to.your/pancake/admin/settings/oauth2gmail
.For more detailed information, check out Using Gmail with XOAUTH2. It's not related to Pancake, but it has screenshots on how to create and set up an app in the Google Developer Console.