Add support for ~validate in OpenAPI3 Importer

[cuminandpaprika]

Please do not post any internal, closed source snippets on this public issue tracker!

Initial request

sysl-go codegen recognises the ~validate attribute on custom datatypes, to generate a validating JSON unmarhsaller.
Is it possible to have the openapi3 sysl importer add this attribute to the schema?

Purpose

Add support for type validation fields in importer so that the generated code can validate these fields

Suggested approaches

What have you tried, and how might this problem be solved?

[andrewemeryanz]

I really think this is out of scope for the importer. I've created a separate ticket on Sysl-go to track an alternative approach:
https://github.com/anzx/sysl-go/issues/163