Per commit review may be easier
- clean up type hints that were getting confusing
- add remembering of names so we can log that and help debugging
- check all USNs of 'add' changes to see if lookup has them (done in batches)
- remove 'add' changes if the USN is missing from lookup
- don't create groups if there is nothing to add now
Makes no sense filtering 'remove' changes as these will only exist if the USN was already found in lookup group.
Closes: #6 (closed)