OAS 3.1 Support

[grokify]

OAS 3.1 has some changes from OAS 3.0:

• OAI Oerview: https://www.openapis.org/blog/2021/02/16/migrating-from-openapi-3-0-to-3-1-0
• APIMatic Overview: https://www.apimatic.io/blog/2021/09/migrating-to-and-from-openapi-3-1
• Kin OpenAPI Go Module: https://github.com/getkin/kin-openapi/issues/230
• Huma Go Module: https://github.com/danielgtaylor/huma
• libopenapi Go Module: https://github.com/pb33f/libopenapi