The old flow encrypted the guest password on disk next to its own key,
then sent it to the guest in the bootstrap HTML anyway. Now redemption
mints the session with ISessionManager.AuthenticateDirect and the page
only ever carries the session token. The guest account still gets a
random password nobody knows, so blank login stays impossible, but no
password is stored or sent anywhere anymore. Cleanup now defaults to
every 30 minutes instead of daily at 4am so expired guests die fast.
Includes fix for redemption failing with DbUpdateConcurrencyException:
change the guest password before applying the user policy, since
UpdatePolicyAsync bumps the user's EF concurrency token and a stale
instance then breaks ChangePassword.
Franciskid