Document how to generate long-lasting token for Google Drive access

[jpmckinney]

I downloaded the JSON file from https://console.cloud.google.com/apis/credentials?referrer=search&orgonly=true&project=pelican-289615&supportedpurview=organizationId

I followed the steps at https://stackoverflow.com/questions/66069065/how-to-get-new-refresh-google-oauth-token, i.e.:

Open in a browser (replacing [client-id]) https://accounts.google.com/o/oauth2/auth?client_id=[client-id]&redirect_uri=http://localhost&scope=https://www.googleapis.com/auth/documents%20https://www.googleapis.com/auth/drive&response_type=code&approval_prompt=force&access_type=offline

Then run (replacing bracketed terms):

curl \
  -d "client_id=[client-id]" \
  -d "client_secret=[client-secret]" \
  -d "redirect_uri=http://localhost" \
  -d "grant_type=authorization_code" \
  -d "code=[code-from-redirect-url-above]" \
  "https://www.googleapis.com/oauth2/v4/token"

This yields a token that lasts 1 hour only.

Going through the git history for token.pickle, I found a JSON document like:

{"token": "[token]", "refresh_token": "[refresh_token]", "token_uri": "https://oauth2.googleapis.com/token", "client_id": "[different-client-id]", "client_secret": "[different-client-secret]", "scopes": ["https://www.googleapis.com/auth/documents", "https://www.googleapis.com/auth/drive"]}

It no longer worked, however.

Related: #118