Consider using the gargle library for Google authentication

https://github.com/r-lib/gargle is a toolkit for handling authentication with Google resources, and it
provided features similar to your R/register_google.R

With Gargle, you'd be able to drop a lot of the code that you currently have to maintain in your package, while not having to worry about always doing the right thing.

This vignette describes how you create an authentication function for your package.
https://gargle.r-lib.org/articles/gargle-auth-in-client-package.html

Best wishes,
Michael

Read R/register_google.R and the linked gargle-auth-in-client-package vignette first. Compare the package’s current Google authentication approach with gargle’s client-package pattern; done would require an agreed migration scope and a complete authentication implementation that replaces the maintained code where appropriate.

Written by the indexing model from the issue text.