Add Device Code authorization to the supported OAuth Flows

[LikeLakers2]

Clone of PR #2401, resubmitted against the v3.2.0-dev branch as requested by webron. Note that this is not submitted against the main branch, but I will happily resubmit it against the main branch upon request.

Description of the original PR follows, with some extraneous details edited out:

---

Closes#2381.

This is a PR for the Device Authorization OAuth Flow, based on RFC8628. I suggested this over at #2381 and was asked to make a PR for it.

The URL used for this flow is named deviceAuthorizationUrl, separate from authorizationUrl as the two have completely different semantics and usages, so I was concerned that using authorizationUrl for both might be confusing. That said, I would be happy to merge this into authorizationUrl if requested.

[karenetheridge]

I see that schemas/v3.2 doesn't exist yet, but if this PR is accepted, some schema changes should be made as well.

[LikeLakers2]

@karenetheridge Apologies for taking so long to respond, but are you suggesting I should create (and edit appropriately) the v3.2 schema folder? Or is that simply a note for whomever reviews this PR?

[karenetheridge]

Yes, I think the v3.2 schema folder (with schemas) should be created in the v3.2.0-dev branch (by the maintainers), so you can merge your changes on top.

[ericallam]

Checked this change against https://datatracker.ietf.org/doc/html/rfc8628 and also a real world usage on GitHub REST Device Flow and it all looks good.

[MikeRalphson]

@karenetheridge as the markdown is the source of truth and the schema a (mere) artifact (though a useful one), it's normal that the creation / update of the schema can lag the creation of a new dev branch and initial changes.

[MikeRalphson]

LGTM - thanks.