feat(label): support configurable exclusive label sets

[anshulchikhale30-p]

#179

What this PR does

This PR adds support for configurable exclusive label prefixes in the label plugin.

When a label matching an exclusive prefix is added, any existing label with the same prefix on the issue or PR is automatically removed.

Example

Current labels:
priority/backlog
kind/bug

User adds:
/priority important-soon

↓

Automatically remove:

priority/backlog

↓

Final labels:

priority/important-soon
kind/bug

Changes

• Add ExclusiveLabelPrefixes to the label plugin configuration.
• Merge exclusive label prefixes during config merging.
• Remove conflicting labels before applying a new exclusive label.
• Add unit tests for the new behavior.
• Document the new configuration option.

Testing

go test ./pkg/plugins/label
go test ./pkg/plugins

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[kubernetes-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: anshulchikhale30-p
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Details

Needs approval from an approver in each of these files:

• pkg/plugins/OWNERS

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[kubernetes-prow]

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[kubernetes-prow]

Hi @anshulchikhale30-p. 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.

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[anshulchikhale30-p]

/cc @jberkus

[stmcginnis]

/retitle feat(label): support configurable exclusive label sets