chore: attempt deep defaults in spec factory

[nickofthyme]

Attempt at deep defaults.

Findings:

• The types would be loose but the values are all typed going into the spec factory so shouldn't be too concerning
• The props would need to be overridden before passing the the upsertSpec function which is not idea.
• The breaking point for me was the domain having partial keys. So either I make the whole domain partial on the spec causing type checks everywhere. Or we somehow find a way to type which props are objects whose keys can be deep and values can be partials.

All in all this really hurt my brain and I think it's a future consideration when we separate the final spec types from the props the user must defined which could differ. But currently I think this is more effort than it is worth.