knative: domain: Require cluster match for claim lookup

[Elvand-Lie]

Summary

Require a ClusterDomainClaim to belong to the same cluster as the
DomainMapping before treating it as the corresponding claim.

Problem

The DomainMapping list can display resources from multiple selected clusters.
It also loads ClusterDomainClaims across those clusters.

getClusterDomainClaim() previously decided whether cluster matching was
needed from a locally created one-element array:

const clusters = [cluster];
const requireClusterMatch = clusters.length > 1;

Because that condition was always false, the lookup matched only the hostname
and target namespace.

If cluster A contained a claim for shop.example.com targeting namespace
store, an identically named DomainMapping in cluster B could incorrectly
display that claim as present. The action for creating the actually missing
claim in cluster B could consequently be hidden.

Fix

Match claims using all three relationship dimensions:

• cluster
• hostname
• target namespace

The helper remains compatible with callers where the DomainMapping does not
carry a cluster directly by using the caller-provided cluster as its effective
cluster.

The lookup no longer mutates the returned claim.

Testing

Added focused tests covering:

• rejection of a claim from another cluster;
• successful same-cluster matching;
• correct selection when both clusters contain the same hostname and namespace;
• rejection and non-mutation of a clusterless claim;
• fallback to the caller cluster when the DomainMapping has no cluster;
• unloaded claims;
• blank and absent DomainMapping hosts.

The cross-cluster regression test fails against the previous implementation
and passes with this change.

Verification

• npm run tsc
• npm run lint
• npm run format
• npm run test
• npm run build
• git diff --check

All checks passed.

[illume]

Thanks for this PR.

A few of the commits don't quite follow the project guidelines. We use Linux kernel style for git commits — have a look at the contributing guide and previous commits with git log.

Commits that need attention

• knative: require cluster match for DomainMapping claims — Description must start with a capital letter — e.g. frontend: HomeButton: Fix the button not frontend: HomeButton: fix the button.

Commit guidelines

• Use atomic commits focused on a single change.
• Use the title format <area>: <Description of changes> — description must start with a capital letter.
• Keep the title under 72 characters (soft requirement).
• Explain the intention and why the change is needed.
• Make commit titles meaningful and describe what changed.
• Do not add code that a later commit rewrites; squash or reorder commits instead.
• Do not include Fixes #NN in commit messages.

Good examples:

• frontend: HomeButton: Fix so it navigates to home
• backend: config: Add enable-dynamic-clusters flag

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused implementation correctly addresses the cross-cluster lookup bug and includes comprehensive regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Ensures DomainMappings only match ClusterDomainClaims from the same cluster.

Changes:

• Enforces cluster, hostname, and namespace matching without mutating claims.
• Adds focused regression and edge-case tests.

File	Description
knative/​src/​utils/​domain.ts	Enforces strict cluster-aware claim lookup.
knative/​src/​utils/​domain.test.ts	Tests cross-cluster matching and fallback behavior.

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[Elvand-Lie]

@illume Rebased and revised to address the review feedback and commit-history requirements. The branch is now a single atomic commit and has been re-verified. Ready for another look.