Github Oauth scope

[SimonLab]

Currently the scope used for Github oauth is defined manually:

auth/lib/auth_web/controllers/auth_controller.ex

Line 65 in e121667

oauth_github_url = ElixirAuthGithub.login_url(%{scopes: ["user:email"], state: referer})

However with our Labels application we want to allow users to login with Github and to be able to add/remove labels from repositories. This means that we need a way for the auth app to define which scopes to allow for the applications.

List of Github scopes: https://docs.github.com/en/developers/apps/building-oauth-apps/scopes-for-oauth-apps

[nelsonic]

@SimonLab if we want to allow Apps to define their OAuth Scopes dynamically ... this might end up being a bit more work.