Webhook converter fails if object being converted is missing metadata

[ncdc]

What happened?

Because of #117356, the webhook converter may receive an object to convert that has no metadata. In that scenario, it returns an error, because it expects the input object to have metadata.

What did you expect to happen?

No error

How can we reproduce it (as minimally and precisely as possible)?

https://github.com/LittleWat/conversion-webhook-test-with-flux

Anything else we need to know?

Ideally the converter should always receive an object with metadata. Until then, it should match its output expectations to the input object; i.e., if the input does not have metadata, it should not require that the output does have it.

Kubernetes version

```console $ kubectl version # paste output here ```

Cloud provider

OS version

```console # On Linux: $ cat /etc/os-release # paste output here $ uname -a # paste output here # On Windows: C:\> wmic os get Caption, Version, BuildNumber, OSArchitecture # paste output here ```

Install tools

Container runtime (CRI) and version (if applicable)

Related plugins (CNI, CSI, ...) and versions (if applicable)

[k8s-triage-robot]

This issue is labeled with priority/important-soon but has not been updated in over 90 days, and should be re-triaged. Important-soon issues must be staffed and worked on either currently, or very soon, ideally in time for the next release.

You can:

• Confirm that this issue is still relevant with /triage accepted (org members only)
• Deprioritize it with /priority important-longterm or /priority backlog
• Close this issue with /close

For more details on the triage process, see https://www.kubernetes.dev/docs/guide/issue-triage/

/remove-triage accepted

[jiahuif]

/assign @Jefftree /triage accepted

[k8s-triage-robot]

This issue is labeled with priority/important-soon but has not been updated in over 90 days, and should be re-triaged. Important-soon issues must be staffed and worked on either currently, or very soon, ideally in time for the next release.

You can:

• Confirm that this issue is still relevant with /triage accepted (org members only)
• Deprioritize it with /priority important-longterm or /priority backlog
• Close this issue with /close

For more details on the triage process, see https://www.kubernetes.dev/docs/guide/issue-triage/

/remove-triage accepted

[jiahuif]

/triage accepted

[k8s-triage-robot]

This issue is labeled with priority/important-soon but has not been updated in over 90 days, and should be re-triaged. Important-soon issues must be staffed and worked on either currently, or very soon, ideally in time for the next release.

You can:

• Confirm that this issue is still relevant with /triage accepted (org members only)
• Deprioritize it with /priority important-longterm or /priority backlog
• Close this issue with /close

For more details on the triage process, see https://www.kubernetes.dev/docs/guide/issue-triage/

/remove-triage accepted

[BenTheElder]

@liggitt should we keep this accepted or close it?

[cici37]

/assign @jpbetz Thanks :) /triage accepted

[k8s-triage-robot]

This issue is labeled with priority/important-soon but has not been updated in over 90 days, and should be re-triaged. Important-soon issues must be staffed and worked on either currently, or very soon, ideally in time for the next release.

You can:

• Confirm that this issue is still relevant with /triage accepted (org members only)
• Deprioritize it with /priority important-longterm or /priority backlog
• Close this issue with /close

For more details on the triage process, see https://www.kubernetes.dev/docs/guide/issue-triage/

/remove-triage accepted

[Jefftree]

/assign @seans3 /triage accepted