* `v1beta1` RoleBinding/ClusterRoleBinding subjects changed `apiVersion` to `apiGroup` to fully-qualify a subject. ServiceAccount subjects default to an apiGroup of `""`, User and Group subjects default to an apiGroup of `"rbac.authorization.k8s.io"`. ([#41184](https://github.com/kubernetes/kubernetes/pull/41184), [@liggitt](https://github.com/liggitt))

### Action Required

* `kubectl create rolebinding` and `kubectl create clusterrolebinding` no longer allow specifying multiple subjects as comma-separated arguments. Use repeated `--user`, `--group`, or `--serviceaccount` arguments to specify multiple subjects.  ([#43903](https://github.com/kubernetes/kubernetes/pull/43903), [@xilabao](https://github.com/xilabao))

### Other notable changes

- This PR will leverage subtests on the existing table tests for the scheduler units. ([#63665](https://github.com/kubernetes/kubernetes/pull/63665), [@xchapter7x](https://github.com/xchapter7x))

* RBAC objects are now stored in etcd in v1 format. After completing an upgrade to 1.9, RBAC objects (Roles, RoleBindings, ClusterRoles, ClusterRoleBindings) should be migrated...

  `delete`, `describe`, `edit`, `get`, `label,` and `set`. `--include-uninitialized=true` makes
  kubectl commands apply to uninitialized objects, which by default are ignored
  if the names of the objects are not provided. `--all` also makes kubectl
  commands apply to uninitialized objects. See the
  [initializer documentation](https://kubernetes.io/docs/admin/extensible-admission-controllers/) for more details.

* The `--remove-extra-subjects` and `--remove-extra-permissions` flags have been enabled for `kubectl auth reconcile` ([#64541](https://github.com/kubernetes/kubernetes/pull/64541), [@mrogers950](https://github.com/mrogers950))

#### Other API changes:

- Kubectl set resources will no longer return an error if passed an empty change for a resource. kubectl set subject will no longer return an error if passed an empty change for a resource. ([#85490](https://github.com/kubernetes/kubernetes/pull/85490), [@sallyom](https://github.com/sallyom))

- Kubernetes components that accepted X.509 client certificate authentication now read the user UID from a certificate subject name RDN with object ID `1.3.6.1.4.1.57683.2`. An RDN with this object ID had to contain a string value and appear no more than once in the certificate subject. Reading the user UID from this RDN could be disabled by setting the beta feature gate `AllowParsingUserUIDFromCertAuth` to `false`(until the feature gate graduated to...

- AWS cloud provider supports auto-discovering subnets without any `kubernetes.io/cluster/<clusterName>` tags. It also supports additional service annotation `service.beta.kubernetes.io/aws-load-balancer-subnets` to manually configure the subnets. ([#97431](https://github.com/kubernetes/kubernetes/pull/97431), [@kishorj](https://github.com/kishorj))