Support OpenAPI 3.1

[Jean85]

OpenAPI 3.1 has just been released... Can we hope for support in this library?

Changes in the spec seems really small, but there are some small BCs that could complicate the stuff further: https://www.openapis.org/blog/2021/02/16/migrating-from-openapi-3-0-to-3-1-0

Main differences:

• no more nullable

-type: string
-nullable: true
+type:
+ - "string"
+ - "null" 

• exclusiveMinimum and exclusiveMaximum are used directly

-minimum: 7
-exclusiveMinimum: true
+exclusiveMinimum: 7

• examples, no more example

-example: fedora
+examples:
+ - fedora

• Describing File Upload Payloads
• declaring JSON Schema dialect explicitly

[WyriHaximus]

Just opened #117 that adds the low level schema validation, already have code lined up to take care of the no more nullable as well, plus #114 for webhooks as well. But both depends on #117 to kick this all off

[Jean85]

Any news here? How can we help to push this forward?