Allow to pick a specific user from gh CLI to work in GH EMU scenarios

[nfx]

Invoke gh auth token ... --user ... if the special parameter is added to provider conf. Otherwise gh auth token will give the token for the user that did last gh auth login command

[nfx]

@nickfloyd what should be the name for the provider attribute here and the default env var? will fix the linters after that

[kfcampbell]

Hmm...I'm somewhat partial to gh_cli_user as it makes it clear the authentication is coming from the gh CLI in the normal scenario. Thoughts?

[nfx]

@kfcampbell this functionality is required when you have more than one user authenticated, eg EMU