- Introduce support for CEL optionals (see [CEL spec proposal 246](https://github.com/google/cel-spec/wiki/proposal-246)).
  This feature will not be fully enabled until a future Kubernetes release (likely to be v1.29), but is added in v1.28 to enable

- client-go

For more information on release notes see: https://git.k8s.io/community/contributors/guide/release-notes.md
-->
```release-note

```

#### Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

<!--
This section can be blank if this pull request does not require a release note.

When adding links which point to resources within git repositories, like

 
## Changes by Kind

### Deprecation

- #### Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:
  
  <!--
  This section can be blank if this pull request does not require a release note.
  
  When adding links which point to resources within git repositories, like

### API Change

- #### Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:
  
  <!--
  This section can be blank if this pull request does not require a release note.
  
  When adding links which point to resources within git repositories, like

- ```
  
  #### Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.: ([#125272](https://github.com/kubernetes/kubernetes/pull/125272), [@mauri870](https://github.com/mauri870))