We won't be implementing IMAP UNAUTHENTICATE.

Doesn't seem like it's a common thing to do. And it's just a bit risky, it's
too easy to forget to clear some part of the authentication state on a
connection (especially future changes that forget to update clear a new field
during unauthenticate). If a strong use case ever pops up, we can reconsider.

Also update the roadmap a bit.

README.md

@@ -141,9 +141,10 @@ https://nlnet.nl/project/Mox/.
 - Automate DNS management, for setup and maintenance, such as DANE/DKIM key rotation
 - Config options for "transactional email domains", for which mox will only
   send messages
-- More IMAP extensions (UNAUTHENTICATE, NOTIFY, OBJECTID, UIDONLY)
+- More IMAP extensions (NOTIFY, UIDONLY)
 - Encrypted storage of files (email messages, TLS keys), also with per account keys
 - Recognize common deliverability issues and help postmasters solve them
+- JMAP, IMAP OBJECTID extension, IMAP JMAPACCESS extension
 - Calendaring with CalDAV/iCal
 - Introbox, to which first-time senders are delivered
 - Add special IMAP mailbox ("Queue?") that contains queued but
@@ -160,7 +161,6 @@ https://nlnet.nl/project/Mox/.
 - Privilege separation, isolating parts of the application to more restricted
   sandbox (e.g. new unauthenticated connections)
 - Using mox as backup MX
-- JMAP
 - Sieve for filtering (for now see Rulesets in the account config)
 - ARC, with forwarded email from trusted source
 - Milter support, for integration with external tools