We authorize a user visiting our website using OAuth2 and Google; We get hold of her/his access token that Google returns; There is a Google Apps Script web app that is executed as the user running the web app; We want to call this app (3) by providing the access token (2) so Google not to ask again for authorization; Actually, we want to call this app (3) not by redirecting the user to it but by calling it as a web service.
https://developers.google.com/apps-script/add-ons/how-tos/non-google-services
