KEP 1645: relax the ServiceExportConflict requirements

[tpantelis]

The KEP states that "a ServiceExportConflict condition will be set on all ServiceExports for the conflicted service", however this assumes an implementation has a central controller that has access to all the constituent ServiceExports or that each cluster has access to the ServiceExports on every other cluster but this may not be the case.

This PR modifies the language to recommend the condition be set on all ServiceExports but not require it.

See the motivation and further discussion here: https://github.com/kubernetes-sigs/mcs-api/pull/111#discussion_r2162096079

Issue link: Multi-Cluster Services API #1645

[tpantelis]

/cc @MrFreezeex

[k8s-ci-robot]

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[mikemorris]

/lgtm

Discussed in June 25th, 2025 SIG-Multicluster meeting, see notes at https://docs.google.com/document/d/18mk62nOXE_MCSSnb4yJD_8UadtzJrYyJxFwbrgabHe8/edit?tab=t.0#heading=h.gxm49ag2wja7

Thanks for updating this - definitely makes sense that the original language would have been much easier to implement in a centralized model.

[tpantelis]

/cc @lauralorenz

[skitt]

This looks good to me too, but if I approve it it will merge immediately, I would like feedback from more participants in the discussion :wink:.

[tpantelis]

Based on discussion in the SIG meeting, the consensus is to keep the current language in the KEP wrt to conflict conditions and possibly make adjustments to ServiceImport to facilitate implementation if needed.