[pipes] consider generating Pipes JSON schemas from Pydantic models

[danielgafni]

What's the use case?

Pydantic has this nice feature for generating JSON schemas from models.

It sounds like it would be a very good way to define Pipes types.

To be clear, the Python dagster-pipes package won't have to depend on pydantic. It would only be used to generate the schemas, which in turn could be used to implement and validate Pipes data structures across all programming languages.

Ideas of implementation

Should be straightforward

Additional information

Currently the JSON schemas live here. They should be moved to the main repo so that we can use them inside Dagster itself.

Message from the maintainers

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cc @cmpadden @marijncv @schrockn