* Change `kubeadm create token` to default to the group that almost everyone will want to use.  The group is system:bootstrappers:kubeadm:default-node-token and is the group that kubeadm sets up, via an RBAC binding, for auto-approval (system:certificates.k8s.io:certificatesigningrequests:nodeclient). ([#53512](https://github.com/kubernetes/kubernetes/pull/53512), [@jbeda](https://github.com/jbeda))

## Changelog since v1.15.3

### Other notable changes

* Restores compatibility with kubectl client-side validation when structural schemas are present in a CRD which sets spec.preserveUnknownFields=true ([#82666](https://github.com/kubernetes/kubernetes/pull/82666), [@liggitt](https://github.com/liggitt))

          <type>String</type>
          <required>true</required>
          <description>The unique id for this report set, to be used during POM inheritance and profile injection
            for merging of report sets.
          </description>
          <defaultValue>default</defaultValue>
        </field>
        <field>
          <name>reports</name>
          <version>4.0.0+</version>

### Other (Cleanup or Flake)

- Kube-apiserver: sets an upper-bound on the lifetime of idle keep-alive connections and time to read the headers of incoming requests ([#103958](https://github.com/kubernetes/kubernetes/pull/103958), [@liggitt](https://github.com/liggitt)) [SIG API Machinery and Node]

              host:
                description: The name of a service from the service registry.
                type: string
              subsets:
                description: One or more named sets that represent individual versions
                  of a service.
                items:
                  properties:
                    labels:
                      additionalProperties:

*   `tf.experimental.dtensor`

    *   Deprecated `dtensor.run_on` in favor of `dtensor.default_mesh` to correctly indicate that the context does not override the mesh that the ops and functions will run on, it only sets a fallback default mesh.

### Other (Cleanup or Flake)

- Kube-apiserver: sets an upper-bound on the lifetime of idle keep-alive connections and time to read the headers of incoming requests ([#103958](https://github.com/kubernetes/kubernetes/pull/103958), [@liggitt](https://github.com/liggitt)) [SIG API Machinery and Node]

* 📝 Fix example code with sets in Tutorial - Body - Nested Models 3. PR [#2054](https://github.com/tiangolo/fastapi/pull/2054) by [@hitrust](https://github.com/hitrust).
* 📝 Fix example code with sets in Tutorial - Body - Nested Models 2. PR [#2053](https://github.com/tiangolo/fastapi/pull/2053) by [@hitrust](https://github.com/hitrust).

- kubeadm now properly recognizes Docker 18.09.0 and newer, but still treats 18.06 as the default supported version.
- kubeadm now automatically sets the `--pod-infra-container-image` flag when starting the kubelet.

### SIG IBM Cloud

- Added a `--topology-manager-policy-options` flag to the kubelet to support fine tuning the topology manager policies. The first policy option, `prefer-closest-numa-nodes`, allows these policies to favor sets of NUMA nodes with shorter distance between nodes when making admission decisions. ([#112914](https://github.com/kubernetes/kubernetes/pull/112914), [@PiotrProkop](https://github.com/PiotrProkop))