OAS 3.1 Initial support - Schema properties support in annotations - Enhanced Response Schema resolving

[frantuma]

OAS 3.1 Initial support

This PR introduces support for OAS 3.1 representation (swagger-models), serialization and deserialization.

Changes aim to be backward compatible, therefore no code changes should be needed in clients. New OAS 3.1 constructs in swagger-models are annotated with @OpenAPI31 and additional helper classes Json31 and Yaml31 have been added to provide OAS 3.1 serialization / deserialization. Please see deserialization and serialization examples for usage scenarios.

References #3913

Support for schema properties resolution from annotations

this commit introduces support to define Schema properties via annotations. Please see this and this examples for usage scenarios.

Related tickets: #3633, #3547, #2891, #3433

Support for existing response schema resolving from method return type.

this commit introduces support to resolve a response schema from the method return type also for responses defined via @ApiResponse annotations. Please see this example for usage scenarios.

References #3870

[antonlisovenko-toast]

@frantuma thanks for the PR, this is really helpful, am I right that this adds support only when ApiResponse is used only as a standalone annotation (@ApiResponse) rather than a part of responses in @Operation?
Trying this and it's not working:

@Operation(
        responses = [
            ApiResponse(responseCode = "200", useReturnTypeSchema = true),
            ApiResponse(responseCode = "422", description = "User already has restaurant access")
        ]