Support GitHub Enterprise

[bn-d]

Currently the host and scheme is hard coded at

ocaml-github/lib/github_core.ml

Line 177 in 91edfae

let entry_uri = "https://github.com/login/oauth/authorize" in

I would be great if we can add support for GitHub Enterprise Server.

i.e.

let authorize
  ?(scheme="https")
  ?(host="github.com")
  ...
  =
  ...
  Uri.make ~scheme ~host ~path:"login/oauth/access_token" ~query ()

[tmcgilchrist]

👍🏻 PRs very welcome to do this.

A good place to start would be extending Github_s.Env to include this information.