Change what happens when an SOA is deleted
Get rid of override_soa junk
Add a couple comments
Marginally improve Nameserver cleaning efficiency
Add another helpful comment
Stop set_soa_recursive at delegation boundaries
Fix spelling
Remove now-superfluous full_clean call
Sort of make new test pass
Add comments; make test actually pass
Don't pre-evaluate queryset -- it's not going to change
Don't stop recursive SOA assignment at delegated domains
Ensure domain can't have SOA whose root is below it
Remove useless line
Flip SOA assignment order (pre- to post-order)
Get rid of check_for_soa_partition; re-add validate_zone_soa

check_for_soa_partition is redundant; validate_zone_soa is important for
preventing illegal 'soa' values.
Improve comment
Move zone validation to Domain.clean
Remove grossly incorrect comment
Move validation to save (it requires a primary key)