[migration] make sure the repo knows about all constraint types
Adding new constraint types is cumbersome. It's easy to forget to do it
in a migration script. So sync the constraint types at the beginning of
each migration.
Closes #3724892
change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')