pydantic based netcdf input schema

[mjreno]

MODFLOW 6 NetCDF input schema with validation interface

• validate meta dictionaries describing a NetCDF input file
• generate jsonschema dictionaries directly from schema

[wpbonelli]

Suggest consistent naming of the user-facing model and package config objects, maybe dropping "Cfg" and "Input" and just calling them NetCDFModel and NetCDFPackage?

Just to mention for passersby, we discussed offline it would be nice if there were a single object model whose structure matches the schema and which exposes a template construction API via e.g. classmethods, instead of having two parallel object models, one schema, one user-facing. But I know you were still looking at the feasibility of that and it may come later

[mjreno]

Aligning the names is a good idea- I'm fine with your suggestion or suffixing both with "Input" just to clearly distinguish scope. Maybe we should chat once more about the conceptual alignment, I think things are set up to take that step and it is probably a good time to consider doing it.

[wpbonelli]

I didn't look at the other PR against the dfn branch, presumably the differences are minimal. Reviewing this one because it will be the more "public" of the two for now.