I am creating a Sheets add-on that works with our app. Our app uses Google OAuth for authentication.
I have the add-on working with manually configured credentials, but obviously that's not a real life solution. Now I need to have the add-on user authenticate to our app within the add-on itself, so we know whose account to work with.
User has data in Sheets -> user uses add-on to authenticate to app -> add-on uses app's API to push/pull data between Sheets and app for that user
I have tried using our API's login URL to get the HTTPResponse from Google using fetch() and loading it into a sidebar, but aside from it being ugly, it doesn't give me the expected option of choosing the Google account I want, but rather logging in from scratch, and when I enter my Google account, it doesn't do anything other than continue giving me errors about the frame being sandboxed. The threads here and here don't seem to address the issues as they're talking about iframe within the app, whereas I'm trying to use the sidebar in Sheets itself.
The app and the add-on are using the same GCP Project ID.
I need to get the same BearerToken that the app uses to use in the add-on.
