Currently the implementation does not verify that a 200 response is received
before attempting to parse the JSON response.
This PR updates the behaviour to fail with an authorization error, similar to
how other auth library implementations.
- adds no new functionality beyond the initial attempt at providing
Usable Auth constructors.
- adds enough packaging metadata to be able to export this library as a gem.
- next steps:
complete usable auth implemntation of Application Default Credentials.
Tim Emiola