Add OAuth bearer auth-info support (#1233)

[Swastik092]

Add end-to-end OAuth Bearer support for shared queues: the scheduler now understands the bearer auth-info keyword, advertises the OAuth metadata via DNS-SD and destination data, and persists bearer tokens. The IPP backend requests the new attributes, honors WWW-Authenticate: Bearer, and forwards AUTH_BEARER tokens. Docs and man pages were updated, and the change is recorded in CHANGES.md.

[michaelrsweet]

Fantastic, thanks for tackling this!

ATM I am trying to fix the CI server tests, but once that is finished up I will get to reviewing this and providing feedback!