GET a URL with a GitHub token, falling back to an unauthenticated request
Source:R/Require-helpers.R
GETWauthThenNonAuth.RdSigns the request with httr::add_headers(Authorization = token) when a
token is supplied, and retries without credentials if GitHub rejects them or
returns a 404. token must carry the "token " prefix that
getGitCredsToken() produces – a bare PAT authenticates nothing.
Usage
GETWauthThenNonAuth(url, token, verbose = getOption("Require.verbose"))