`rsconnect login` using OAuth flow and DCR

[nealrichardson]

Connect 2026.02.0 adds an OAuth server: https://docs.posit.co/connect/admin/authentication/oauth-clients/

Can we use this to get a token? Refresh a token? Without requiring API keys

[atheriel]

Don't forget to stick it into the system keyring. I think the Publisher does that under some conditions, and we could also make the rsconnect package use the same keyring entry, too.