- K8s.io/apimachinery - scheme.Convert() now uses only explicitly registered conversions - default reflection based conversion is no longer available. `+k8s:conversion-gen` tags can be used with the `k8s.io/code-generator` component to generate conversions. ([#90018](https://github.com/kubernetes/kubernetes/pull/90018), [@wojtek-t](https://github.com/wojtek-t)) [SIG API Machinery, Apps and Testing]

- Fixed a deep copy issue when retrieving the controller reference. ([#124116](https://github.com/kubernetes/kubernetes/pull/124116), [@HiranmoyChowdhury](https://github.com/HiranmoyChowdhury)) [SIG API Machinery and Release]
- Fixed code-generator client-gen to work with `api/v1`-like package structure. ([#125162](https://github.com/kubernetes/kubernetes/pull/125162), [@sttts](https://github.com/sttts)) [SIG API Machinery and Apps]

- Remove support for `node-expansion` between `node-stage` and `node-publish` ([#108614](https://github.com/kubernetes/kubernetes/pull/108614), [@gnufied](https://github.com/gnufied))
- Removed deprecated `generator` and `container-port` flags ([#106824](https://github.com/kubernetes/kubernetes/pull/106824), [@lauchokyip](https://github.com/lauchokyip))

OpenAPI specs for native types have long been served at /openapi/v2, and they are consumed by a number of components, notably kubectl client-side validation, kubectl explain and OpenAPI based client generators.

With Kubernetes 1.15 as beta, OpenAPI schemas are also published for CRDs, as long as their schemas are structural.

These changes are reflected in the following Kubernetes enhancements:

    * The `generate-internal-groups.sh` script in k8s.io/code-generator will generate OpenAPI definitions by default in `pkg/generated/openapi`. Additional API group dependencies can be added via `OPENAPI_EXTRA_PACKAGES=<group>/<version> <group2>/<version2>...`.

repeating the previous list.  The number of identifiers must be equal
to the number of expressions in the previous list.
Together with the <a href="#Iota"><code>iota</code> constant generator</a>
this mechanism permits light-weight declaration of sequential values:
</p>

<pre>
const (
	Sunday = iota
	Monday
	Tuesday
	Wednesday
	Thursday
	Friday
	Partyday