Add Downward API volume fieldRef support for pod metadata files

[Copilot]

InterLink already resolved Downward API fieldRef for env vars, but volume-based Downward API metadata files were incomplete. This PR extends volume handling so pods can mount metadata files from both projected and direct downwardAPI volumes with Kubernetes-standard field paths.

• Downward API field path coverage

  • Added field resolution for volume items:
    • metadata.name, metadata.namespace, metadata.uid
    • metadata.labels, metadata.annotations
    • spec.nodeName, spec.serviceAccountName
    • status.podIP, status.hostIP
  • Kept unsupported selectors as non-fatal (logged and skipped), matching existing behavior.

• Direct downwardAPI volume support

  • Added handling for volumes[].downwardAPI in remoteExecutionHandleVolumes (previously only projected sources were handled for this path).
  • Populates ProjectedVolumeMaps for downstream execution in the same way as other projected sources.

• Deterministic metadata file rendering

  • Implemented stable serialization for metadata.labels / metadata.annotations as newline-delimited key="value" entries with sorted keys for deterministic output.

• Targeted unit coverage

  • Added tests validating:
    • all newly supported fieldRef mappings for projected Downward API sources
    • end-to-end handling of direct downwardAPI volumes

volumes:
  - name: podinfo
    downwardAPI:
      items:
        - path: pod-name
          fieldRef: { fieldPath: metadata.name }
        - path: labels
          fieldRef: { fieldPath: metadata.labels }
        - path: annotations
          fieldRef: { fieldPath: metadata.annotations }

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[dciangot]

@copilot lint action is failing

[Copilot]

@copilot lint action is failing

Fixed. The lint failure was due to staticcheck QF1012 in formatDownwardAPIMetadataMap; I updated the string building to satisfy lint without changing behavior. Addressed in commit d379093.

[Copilot]

Pull request overview

This PR extends InterLink’s Downward API handling for volume-mounted metadata files by resolving additional fieldRef paths and adding support for direct volumes[].downwardAPI (not only projected sources). It also makes label/annotation rendering deterministic to avoid non-reproducible output from map iteration.

Changes:

• Refactors Downward API volume item processing into shared helpers and adds support for more fieldRef paths (incl. labels/annotations, node/service account, pod/host IPs).
• Adds handling for direct DownwardAPI volumes in remoteExecutionHandleVolumes by populating ProjectedVolumeMaps.
• Adds unit tests covering the new field paths and the direct downwardAPI volume path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pkg/virtualkubelet/execute.go	Adds shared Downward API resolution helpers and new handling for direct DownwardAPI volumes.
pkg/virtualkubelet/execute_test.go	Adds tests for the expanded fieldRef mapping and direct downwardAPI volumes.

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