"content": {
                                    "application/json": {
                                        "schema": {
                                            "$ref": "#/components/schemas/HTTPValidationError"
                                        }
                                    }
                                },
                            },

beta and enabled by default. CustomResourceDefinitions with [structural schemas](https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/20190425-structural-openapi.md) now publish schemas in the OpenAPI document served at `/openapi/v2`. CustomResourceDefinitions with non-structural schemas have a `NonStructuralSchema` condition added with details about what needs to be corrected in the validation schema. ([#77825](https://github.com/kubernetes/kubernetes/pull/77825), [@royc...

- The `CustomResourceDefaulting` feature is promoted to beta and enabled by default. Defaults may be specified in structural schemas via the `apiextensions.k8s.io/v1` API. See https://kubernetes.io/docs/tasks/access-kubernetes-api/custom-resources/custom-resource-definitions/#specifying-a-structural-schema for details. ([#81872](https://github.com/kubernetes/kubernetes/pull/81872), [@sttts](https://github.com/sttts))

- Fix performance issue when creating large objects using SSA with fully unspecified schemas (preserveUnknownFields). ([#111914](https://github.com/kubernetes/kubernetes/pull/111914), [@aojea](https://github.com/aojea)) [SIG API Machinery, Auth, CLI, Cloud Provider, Cluster Lifecycle, Instrumentation, Storage and Testing]

- Fixed a bug that prevents kubectl to validate CRDs with schema using x-kubernetes-preserve-unknown-fields on object fields.

- Introduced OpenAPI format support for `k8s-short-name` and `k8s-long-name` in CustomResourceDefinition schemas. ([#132504](https://github.com/kubernetes/kubernetes/pull/132504), [@jpbetz](https://github.com/jpbetz)) [SIG API Machinery, Architecture, Auth, CLI, Cloud Provider, Cluster Lifecycle, Instrumentation, Network, Node, Scheduling and Storage]

- Fixed performance issue when creating large objects using SSA with fully unspecified schemas ( preserveUnknownFields ). ([#111557](https://github.com/kubernetes/kubernetes/pull/111557), [@alexzielenski](https://github.com/alexzielenski))

* kube-apiserver: The `AdmissionConfiguration` type accepted by `--admission-control-config-file` has been promoted to `apiserver.config.k8s.io/v1` with no schema changes. ([#85098](https://github.com/kubernetes/kubernetes/pull/85098), [@liggitt](https://github.com/liggitt))...

  - The `/swaggerapi/*` schema docs, deprecated since 1.7, have been removed in favor of the /openapi/v2 schema docs. ([#72924](https://github.com/kubernetes/kubernetes/pull/72924), [@liggitt](https://github.com/liggitt))

## Changelog since v1.20.11

## Changes by Kind

### API Change

- Kube-apiserver: Fixes handling of CRD schemas containing literal null values in enums (#104990, @liggitt) [SIG API Machinery, Apps and Network]

### Bug or Regression