Consider exposing an auth token/client

[shayneczyzewski]

This request came from a Discord DM with @maksim36ua

He would like to be able to make Google API calls on behalf of a Google-logged-in user against one of their APIs. Exe: https://developers.google.com/sheets/api/quickstart/nodejs This requires a google.auth.OAuth2 client.

In our current Passport implementation, we do get back an accessToken and refreshToken that we can probably store and turn into an Oauth2 client (or just use directly to make API calls): https://github.com/wasp-lang/wasp/blob/main/waspc/data/Generator/templates/server/src/routes/auth/passport/generic/provider.js#L11

Let's consider a good way to store/expose this to enable this use case.