fix: validate taskRef.apiVersion format for custom tasks

[waveywaves]

Changes

add validation to ensure taskRef.apiVersion follows the correct format (group/version) when specified. Previously, invalid apiVersion values like 'invalid-api-version' were accepted, causing PipelineRuns to create unhandled CustomRuns that would timeout. Now Pipeline creation fails immediately with a clear error message when an invalid apiVersion is provided.

Fixes #9044

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Release Notes

NONE

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/apis/pipeline/v1/pipeline_validation.go	99.3%	99.3%	0.0
pkg/apis/pipeline/v1beta1/pipeline_validation.go	99.0%	99.0%	0.0

[waveywaves]

/retest

[waveywaves]

/retest

[aThorp96]

One suggested change, two general questions

Valid formats are "group/version" where group contains at least one dot

Is this strictly true? I know addon api groups conventionally use a dot, but as far as I can tell k8s doesn't pose that as a restriction.

[aThorp96]

Should this also validate that the apiVersion and Kind are registered in the cluster or something? A CustomRun will still be created when the apiVersion and kind dosn't exist in the cluster, however the CustomRun is simply never updated with any status so the pipelinerun times out. E.g. in the below screenshots I modified one of the examples to use a bogus apiVersion which was syntactically correct.

I suppose being registered in the cluster is not sufficient since I've seen people mistakenly use "apiVersion": "tekton.dev/v1", "kind": "Task" in a TaskRef. Maybe that level of validation should be somewhere else? WDYT?

[waveywaves]

your're right kube doesn't strictly require dots in API group names. I've removed that restriction. The validation now only checks for group/version format with non-empty group and version parts. On validating whether the apiVersion/kind is registered in the cluster would be useful, but is a separate concern I beleive, it would require runtime cluster access during admission, which is a bigger change. This PR focuses on catching syntactically invalid apiVersions at the webhook validation level. We could track the runtime check as a follow-up issue ? what do you think ?

[vdemeester]

/approve

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[vdemeester]

/lgtm