phpdoc
Log if we have Wbxml or not in the SENDMAIL command.
Simplify
clean up/add/remove some logging.
We can't limit to collections with synckeys here.

We want the lastsynckey value.
Avoid undefined variable warnings.
This status seems to work better to obtain the desired result.

This needs to trigger the client to reinitialize the syncstate with the server.
Don't remove the collection if it's not refreshed.
Attempt to get a synckey from the cache when adding the collection.

Needed from requests like PING that don't send the synckey, it's
expected to always be operating against the most recent confirmed state.
phpdoc/typehints
Allow for checking of synckey when initializing the state.
Give up early if we know we don't have pingable collections.
comments
Add havePingableCollections() and updatePingableFlag()
Perform the empty pingable check after we initialize the state.

Gives the chance to detect vanished state.
Better variable name, we need lastsynckey here instead of synckey.
Shorter variable name
Persist the pingable flag as well.
Completely rewrite PING handling to use the new collection handler.
Might not have airsyncbasebody, even in 12.1.

When devices send ghosted modify commands, we only have what changed.