When a new version is created, the latest version is updated, then
the new one is made. If making a new one fails (most commonly due to
a name conflict), the latest version is left in a broken state. Set up
the new middleware to revert changes to latest version in this case,
and update the level handler to use the middleware. Also added
warning logs if models do not have editableProperties or postEditableProperties
set.
Can't count on toObject getting called, such as on the '/db/classroom/:handle/levels', which
gets the courses property directly. Use middleware instead.
