Comment #3 on issue 216 by kxepal: Cookie Authentication
Case is when user had been already auth'ed at CouchDB, you has cookie
about, but no credentials. The basic example is CouchDB external process,
which might been called by such user and which required to callback CouchDB
for some additional data: it'll has userctx, cookies, but no user
credentials to request CouchDB behind of scene unless you made by another
user name which may create potentially issues.