OpenApi 3.1 and JSON Schema support

[Jolanrensen]

https://apisyouwonthate.com/blog/openapi-v3-1-and-json-schema/

Looks like openapi 3.1 and JSON schema Draft 2020-12 have been brought together.
We should check we support 3.1 and JSON Schema for type generation, as it looks like some changes have been made from 3.0.