Process parent records on join

[anotherpit]

Currently find() uses processor to cast result records, and join() does not. This PR adds processing to parent records of join() results. Child records still need to be processed.

[devinivy]

join() is often used internally– find would use it, but you'd never call it directly. Can you give an example of a failing case?

[particlebanana]

Yes @anotherpit I need a failing test to show that this fixes it and so we don't get any regressions.