Add auth-info=bearer support

[michaelrsweet]

Need to support OAuth for shared queues, which means also exporting oauth-authorization-server-uri and oauth-authorization-scopes per-printer, along with auth-info=bearer (attribute and TXT record).

Clients need to know to get bearer token for shared printing. Pass it in auth-info. Value can be over 1023 octets which could be a problem...