use new webauthn.util.context_from_environment(fallback=False) mode
use new webauthn.util.context_from_environment(fallback=False) mode

Prefer authn info provided by mod_webauthn even if it says client is anonymous.

This will break if you do not also update webauthn with the requisite
API change which was committed to master last week.

informatics-isi-edu/ermrest,informatics-isi-edu/ermrest