- Added request header UID propagation, behind an alpha `RemoteRequestHeaderUID` feature gate. ([#129081](https://github.com/kubernetes/kubernetes/pull/129081), [@stalz](https://github.com/stlaz)) [SIG API SIG API Machinery, cluster lifecycle, testing]

### Failing Test

- Added a alpha feature, behind the `RelaxedEnvironmentVariableValidation` feature gate.
  When that gate is enabled, Kubernetes allows almost all printable ASCII characters to be used in the names

  `v1beta2/v1beta3/v1`.'
   ([#113275](https://github.com/kubernetes/kubernetes/pull/113275), [@Huang-Wei](https://github.com/Huang-Wei))
- 'Added a `ResourceClaim` API (in the `resource.k8s.io/v1alpha1` API group and
  behind the `DynamicResourceAllocation` feature gate).
  The new API is now more flexible than the existing Device Plugins feature of Kubernetes because it

### Avoiding permanent beta

From Kubernetes 1.20 onwards, SIG Architecture will implement a new policy to transition all REST APIs out of beta within nine months. The idea behind the new policy is to avoid features staying in beta for a long time. Once a new API enters beta, it will have nine months to either:

 - reach GA, and deprecate the beta, or

* Introduce Alpha field `Immutable` in both Secret and ConfigMap objects to mark their contents as immutable. The implementation is hidden behind feature gate `ImmutableEphemeralVolumes` (currently in Alpha stage). ([#86377](https://github.com/kubernetes/kubernetes/pull/86377), [@wojtek-t](https://github.com/wojtek-t))

* Fix kubelet reset liveness probe failure count across pod restart boundaries ([#46371](https://github.com/kubernetes/kubernetes/pull/46371), [@sjenning](https://github.com/sjenning))
* The gce metadata server can be hidden behind a proxy, hiding the kubelet's token. ([#45565](https://github.com/kubernetes/kubernetes/pull/45565), [@Q-Lee](https://github.com/Q-Lee))

  feature gates enabled) that their pods could get stuck in the pending phase when deleted.
  
  Users who maintain controllers which relied on the fact that pods with RestartPolicy=Always
  never enter the Succeeded phase may need to adapt their controllers. This is because as a consequence of 

### Pod Hostname as FQDN graduates to Beta

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