I think this lays most of the foundation for pydantic Producers. In order to build the appropriate model, a
Producer must now set the fields in the top level matching the .build signature.

I still need to:

• Validate the .build/.map arguments are a subset of the model ones (cls.__fields__) and match on type
• Validate no Optional/default None fields or add support for them We should support optional, but the Fingerprint logic mentioned below doesn't exist yet (so will keep in mind)
  • Do we need more entropy or "if dep is Optional and missing, replace Fingerprint.empty() with Fingerprint.identity()"?

In future PRs, I'll take a stab at:

• Support Annotated / View arguments to Producer.build
  • Check the root type can be loaded into a View
• build decorator -> Producer subclass (auto setup fields)