Allow trailing dot for service.spec.externalName

[thz]

What type of PR is this?

/kind bug
/sig network

What this PR does / why we need it:

This PR relaxes the validation of service.spec.externalName to allow a trailing dot. (See #78384 for details).

Which issue(s) this PR fixes:

Fixes #78384

Special notes for your reviewer:

A similar related case, which also relaxed the trailing-dot validation: #74686

Does this PR introduce a user-facing change?:

Allow trailing dots in the externalName of Services of type ExternalName.

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[k8s-ci-robot]

Hi @thz. Thanks for your PR.

I'm waiting for a kubernetes 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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[thz]

cla sent.

[thockin]

Thanks!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: thockin, thz

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[thz]

/retest

[k8s-ci-robot]

@thz: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[vllry]

/ok-to-test