column defaults

[Iain-S]

The current code handles defaults if they come from a PK but not if they come from server-side column defaults.

[mhauru]

This is a really good catch. The new code looks good, there just seems to be a simple failure in one of the old tests.

[Iain-S]

Added poetry.lock to the pre-commit workflow cache key as a change to, e.g., the version of isort we use should trigger a rebuild.