BFN
This doesn't return a value, catch an exception instead.
Enable IMAP folder renaming.
Don't rename if $old == $new.

Outlook sends a rename command with old and new being equal when
the folder is moved to the local "Deleted Items" folder.
First round of rewriting hierarchy handling.

Some EAS clients require a non-changing UID for the folder's
serverid. In Exchange, this is provided by MAPI, but IMAP has
no such capability. Generate and map a uid for each folder and
store it.
Update and add a bunch of new tests.
Remove old test.
Use the new folder uids.
Fix type hint.
These are just ids, not the full folder object.
Use the server object to get the importer.
Update state correctly after a change in hierarchy, don't limit by EAS version.
We need the serverid here, not the uid.
Logging
Allow for changing the backend serverid in the folder object.
Add missing protected member.
Logging tweaks
Fix FOLDERCREATE commands for new serverid/uid changes
Fix FOLDERSYNC commands for new serverid/uid changes.
More serverid/uid changes.