python: Implement version-agnostic Protocol types

[bact]

This PR adds src/shacl2code/lang/templates/python/protocols.py.j2 template to generates Protocol structure types for classes in the generated bindings.

Given two versions of a model (v1 and v2; v2 is backward compatible with v1) to shacl2code to generate Python bindings (one at a time), it will generate two bindings that look similar but v1.SomeClass and v2.SomeClass are considered distinct. They are not sharing a common parent type.

This makes it difficult for a downstream user who wants to write a function like:

def func(x: SomeClass) -> SomeClass: ...

Because if it defines SomeClass as v1.SomeClass, it will be incompatible with v2.SomeClass (and vice versa).

This PR provides the generation of protocols.SomeClass which is a structural type that accepts any class with the same shape (has similar members), so v1.SomeClass and v2.SomeClass can be both accepted, even they are unrelated.

This function will work across all versions of the model (provided that they are keeping backward compatibility to previous versions -- not removing any members in newer versions):

def func(x: protocols.SomeClass) -> protocols.SomeClass: ...

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python.py
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[bact]

This PR may need update after #124 got merged, as the protocols may need to have the new Ontology class too. (Possible to get that from auto-generation, but still need to add a test for confidence)

[bact]

#124 merged. Need to review this PR (may need few revision). Put to draft.

[bact]

@JPEWdev if you plan to release a new version, please go ahead with that.

I just realized that the logic I currently used here to check class compatibility across versions is not working with SPDX 3.0.1 vs SPDX 3.1, due to the reliance on term IRIs.

Now trying to find ways around but please don't take this as a blocker. The JSS alone is worth a release.

[bact]

The versioned IRI issue is now solved by allowing user to choose compact form of class to be used as a discriminator. Classes from SPDX 3.0.1 and SPDX 3.1 can now work with each other (as long as they use context document that produce similar compact form).