Feature/dcf - Device Code Flow Support

[EvieePy]

Description

This PR adds support for Device Code Flow.
DCF has various limitations compared to traditional applications that rely on traditional OAuth 2 authentication with a Client Secret, and as such some internals had to be adjusted to support managing a DCF token.

Mainly the client assumes only one token is ever used (which is what DCF is designed for) and assigns and overrides the internal app token with the provided user token from DCF.

Currently this allows separation of the 2 designs (DCF/Traditional) by adding specific methods to Client to Login/Start, with DCF use-cases in mind (which should be user devices like phones and TVs or home assistants).

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
  • I have updated the changelog with a quick recap of my changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)
• I have read and agree to the Developer Certificate of Origin for this contribution