Support new sidecar containers pattern (KEP-753)

[nak3]

In what area(s)?

/area API /area monitoring /area networking /kind spec

KEP-753 was accepted and will introduce an improvement of the sidecar container pattern. It seems it will be available on k8s 1.28 and so Knative should consider to supporting the feature.

• https://github.com/kubernetes/enhancements/issues/753
• https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/753-sidecar-containers/README.md

I think we should consider two parts for the adaptions:

• a. Support queue-proxy as the new sidecar pattern.
• b. Support multi-container as the new sidecar pattern. (#10821 already asked it).

[dprotaso]

/triage accepted

Looks like we'll hit a min version of k8s 1.28 next April - https://kubernetes.io/releases/patch-releases/#detailed-release-history-for-active-branches

[joke]

Sidecar containers are already supported in istio. Would be great if knative would support them to.