Use Couch session cookie instead of basic auth

[jkuester]

Basic auth on Couch is known to be slowhttps://docs.couchdb.org/en/stable/config/auth.html#chttpd_auth/iterations) depending on your password hashing iterations. Instead of passing basic auth creds on each Couch request, we should consider leveraging a session cookie.

One heavy handed 😅 option here would be to switch to just to Pouch with the http adapter and https://github.com/medic/pouchdb-session-authentication.