JSON API clients should tolerate `null` values for such fields, and treat `null` and `[]` as equivalent in meaning unless specifically documented otherwise for a particular field. ([#44593](https://github.com/kubernetes/kubernetes/pull/44593))

## API Changes
- CustomResourceDefinitions now validate documented API semantics of `x-kubernetes-list-type` and `x-kubernetes-map-type` atomic to reject non-atomic sub-types. ([#84722](https://github.com/kubernetes/kubernetes/pull/84722), [@sttts](https://github.com/sttts))

* In-tree support for openstack credentials is now deprecated. please use the "client-keystone-auth" from the cloud-provider-openstack repository. details on how to use this new capability is documented [here](https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/using-client-keystone-auth.md) ([#64346](https://github.com/kubernetes/kubernetes/pull/64346), [@dims](https://github.com/dims))

  - Health check (liveness & readiness) probes using an HTTPGetAction will no longer follow redirects to different hostnames from the original probe request. Instead, these non-local redirects will be treated as a Success (the documented behavior). In this case an event with reason "ProbeWarning" will be generated, indicating that the redirect was ignored. If you were previously relying on the redirect to run health checks against different endpoints, you will need to perform the...

          to GatewayClass or associated parameters. If implementations choose to propagate
          GatewayClass changes to existing Gateways, that MUST be clearly documented
          by the implementation. \n Whenever one or more Gateways are using a GatewayClass,
          implementations SHOULD add the `gateway-exists-finalizer.gateway.networking.k8s.io`

* Exclude nodes labeled as master from LoadBalancer / NodePort; restores documented behaviour. ([#44745](https://github.com/kubernetes/kubernetes/pull/44745), [@justinsb](https://github.com/justinsb))

### Documentation

- Documented the reason field in CRI API to ensure it equals `OOMKilled` for the containers terminated by OOM killer ([#112977](https://github.com/kubernetes/kubernetes/pull/112977), [@mimowo](https://github.com/mimowo))

## Changes by Kind

### API Change

- Protobuf serialization of metav1.MicroTime timestamps (used in `Lease` and `Event` API objects) has been corrected to truncate to microsecond precision, to match the documented behavior and JSON/YAML serialization. Any existing persisted data is truncated to microsecond when read from etcd. ([#111936](https://github.com/kubernetes/kubernetes/pull/111936), [@haoruan](https://github.com/haoruan)) [SIG API Machinery]

- Protobuf serialization of metav1.MicroTime timestamps (used in `Lease` and `Event` API objects) has been corrected to truncate to microsecond precision, to match the documented behavior and JSON/YAML serialization. Any existing persisted data is truncated to microsecond when read from etcd. ([#111936](https://github.com/kubernetes/kubernetes/pull/111936), [@haoruan](https://github.com/haoruan))

    * PR [#1862](https://github.com/tiangolo/fastapi/pull/1862).
* In `encoders.jsonable_encoder` remove parameter `sqlalchemy_safe`.
    * It was an early hack to allow returning SQLAlchemy models, but it was never documented, and the recommended way is using Pydantic's `orm_mode` as described in the tutorial: [SQL (Relational) Databases](https://fastapi.tiangolo.com/tutorial/sql-databases/).
    * PR [#1864](https://github.com/tiangolo/fastapi/pull/1864).