They are changed to MaybeFields ...Read instead when joining.

Remove joins, use optionalRestrict instead.

Also, remove cabal.project because stack.yaml and package.yaml cover
dependencies already.

Based on the suggestions in
https://kodimensional.dev/space-leak

...when node_id exists in the DB

Warning: this silently avoids insertion of patches when node_id is
missing for some reason in the history.

It's easier to find types and functions that are used in code this
way.