Implement GEP-957: Destination Port Matching.

[cxhiano]

What type of PR is this?
/kind feature
/kind api-change

What this PR does / why we need it:

Implement destination port matching proposed in gep-957

Does this PR introduce a user-facing change?:

- Allow routes to select listeners by port number.

[k8s-ci-robot]

Hi @cxhiano. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[hbagdi]

/ok-to-test
We should add an example (examples/ directory) to make sure we have some CI around it.
We should also add a guide for this. I'm not sure if that has to be part of this PR but I think that should be in the scope of the GEP.

[cxhiano]

Example added. PTAL

Agreed that we could have a guide(probably in a separate PR). Should the guide be centered around Route <> Listener attachment or Route <> custom CRD(e.g. Mesh) attachment? I am not sure though.

[robscott]

Thanks @cxhiano! This mostly LGTM, do you mind creating a follow up issue to track adding docs for this feature?

[cxhiano]

I created #1021 for tracking documentation improvement.

[hbagdi]

/lgtm

[youngnick]

I think this is looking great, aside from the small note about the experimental status of Port in the stable docs.

[robscott]

@cxhiano looks like you need to run hack/update-codegen.sh, otherwise LGTM.

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cxhiano, howardjohn, robscott

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[robscott]

Thanks!

/lgtm