Test on Pydantic v1 and v2

[mattwthompson]

Description

This PR updates the codebase to work with both Pydantic v1 and v2 and also tests each case.

[codecov]

Codecov Report

Merging #165 (8dbf4fa) into main (5a33549) will increase coverage by 0.05%.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

Additional details and impacted files

[j-wags]

LGTM pending test success! The CI matrix is huge now, can we drop the pydantic v1 tests before merging?

[mattwthompson]

I'd prefer one of the following options:

1. Drop v1 from the test matrix and make a release based off of this that is explicitly pydantic =2
2. Keep just one v1 test in the matrix and make a release that stills supports v1 and v2

Does either sound acceptable to you? My preference is to do 2, since BespokeFit and some other downstreams don't yet work on v2, but follow this release up with one that drops v1 once it can

[mattwthompson]

I'm electing to go for option 2 as that allows #164 to slip in to environments that aren't yet updated for Pydantic v2