GitHub REST resources typically return full URLs to fetch related
resources at. We used to parse those URLs to find just the path portion
and pass that in to the `REST()` function, which only accepted paths. By
doing so, we are essential de-constructing a URL just to re-assemble it
again. While re-assembling it for Enterprise, though, we would
accidentally inject an extra `api/v3/` prefix where one was not needed.
The solution is just to use raw URLs as reported by the REST API with
no modifications. This extends the `REST()` function to accept full URLs
in addition to just paths to resources.
`admin:org` is inclusive of `read:org`, so if we find the former listed
in response headers, we can conclude that the token has necessary scopes
instead of letting a warning notice be shown.
`fmt.Errorf` hides information and makes it hard to test for specific
conditions in returned error. Return a structured error instead.
Signed-off-by: Pavel Borzenkov <pavel.borzenkov@gmail.com>
