This is safer than type Limit = Int

This big commit improves the jobs API in a way that now we can
completely abstract away over a JobLog.

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