OAS 3.1.0 support

[n2ygk]

OpenAPI Specification Release 3.1.0 has been released. There may be opportunities for improvements or possible breaking changes.

The specification: http://spec.openapis.org/oas/v3.1.0

The release notes are unfortunately not all in one place and may not fully described all the changes:

• https://github.com/OAI/OpenAPI-Specification/releases/tag/3.1.0-rc0
• https://github.com/OAI/OpenAPI-Specification/releases/tag/3.1.0-rc1
• https://github.com/OAI/OpenAPI-Specification/releases/tag/3.1.0

[auvipy]

related https://www.buymeacoffee.com/relequestual/json-schema-2020-12-released