[WIP] Support union in API server

[mengqiy]

Originally discussed in #278 as an alternative.

We will revisit this in 1.8.

[k8s-github-robot]

This PR hasn't been active in 237 days. Closing this PR. Please reopen if you would like to work towards merging this change, if/when the PR is ready for the next round of review.

cc @apelisse @liggitt @mengqiy

You can add 'keep-open' label to prevent this from happening again, or add a comment to keep it open another 90 days

[mengqiy]

/reopen
reopening this since we still want to support union eventually.

[liggitt]

/uncc

[gkarthiks]

@mengqiy Since we have a KEP process, can we please merge this soon or close this and create a KEP?

[apelisse]

This is tracked in other places and there are a zillion open issues for that already. I don't think we need this one specifically.
/close

[k8s-ci-robot]

@apelisse: Closed this PR.

In response to this:

This is tracked in other places and there are a zillion open issues for that already. I don't think we need this one specifically.
/close

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