Supporting OpenAPI 3.1

Some progress seems to have (finally!) be made on @apidevtools/swagger-parser. There is now a release 10.1.0 that should allow OpenApi 3.1 to be parsed. Does this mean Orval could be updated to be compatible or is there still more that is needed with dependencies?

[OliverDudgeon]

Also the tests pass. I’ve tried it with a few different configs without issues. Seems like an easy upgrade? Maybe give it a few days for any reports to come through on @apidevtools/swagger-parser (it also has a PR that’s been merged since the release so there might be another patch incoming)

[geirsagberg]

Seems like the nullable part of 3.1 is not yet supported? From https://www.openapis.org/blog/2021/02/16/migrating-from-openapi-3-0-to-3-1-0

In line with JSON Schema, the type keyword can now define multiple types for a schema with an array. This is useful new functionality, but has also made nullable redundant. In order to achieve the goal of letting JSON Schema tools understand OpenAPI, it was decided to remove nullable entirely instead of deprecate it.

# OpenAPI v3.0
type: string
nullable: true

# OpenAPI v3.1
type:
- "string"
- "null" 

When I generate code from an OpenAPI 3.1 endpoint, I get nullables as foo: unknown | string