Create hashable BaseModel subclass in order to enforce uniqueItems with Set annotation

[theferrit32]

We just need to define what to use as the hash value that will work across all the models.

https://github.com/pydantic/pydantic/issues/1303#issuecomment-599712964

@ahwagner if are going to go ahead with making every object digestible in the model and serialize algorithm, that could be a good solution to this, we can just use those digests. (with a special case for custom root types with a non-pydantic type as their root, like IRI being a str)

[github-actions[bot]]

This issue was marked stale due to inactivity.

[github-actions[bot]]

This issue was marked stale due to inactivity.

[korikuzma]

@theferrit32 I think this is done here. If you agree, we can close