fix: handle unions properly

guacs commented 9 months ago

Description

This is a rewrite of #412, but it fixes the issues that was there with pydantic v1.

Quoting from the above mentioned PR:

This PR fixes the handling of unions. The use of unwrap_args would result in the incorrect creation of children for the field meta. It would just return a random instance of the union and it fails completely in the case of unions of collection types like list[int] | list[str] where unwrap_args might return (int,) for type_args when in fact we want (list[int], list[str]).