Implement a user-ready authentication workflow

[vermiculus]

The authentication workflow is something gh.el seems to do very, very well. I like the idea of using existing authentication configuration options, but it would be worthwhile creating an interactive workflow that will guide the user through this configuration when we run into #2.

Since it's not wrapping any resources, this seems to be in-scope for ghub.

[vermiculus]

On second thought, it would probably be in the better spirit of ghub (and glab) to only offer the authentication options as opposed to the actual workflow. At least, that's what I've implemented here.

A possible workflow implementation might be as follows:

(defun ghub-authenticate (domain scopes note)
  "Authenticates on DOMAIN with SCOPES using NOTE."
  (unless (ghub--domain-configuration domain :secure)
    (user-error "Refusing to send password over unsafe connection; configure your token in `auth-sources'"))
  (let ((ghub-force-basic-authentication t)
        (ghub-domain domain)
        (user-real-login-name
         (ghub--domain-configuration domain :username)))
    (ghub-post "/authorizations" nil
               `((scopes . ,scopes)
                 (note . ,note)))))

…which reminds me, ghub--domain-configuration should probably be public…

[tarsius]

I have merged an alternative implementation. Could you please redo ghub-authenticate on top of that and open a new issue. Thanks!

[vermiculus]

Done 👍