fix(k8saudit): preserve immutable identity metadata after truncated logs

[kyasbal]

Summary

This PR fixes an issue where Kubernetes audit logs with truncated responses (audit.k8s.io/truncated: "true") caused the manifest generator to lose resource identity metadata, leading subsequent patch logs to be misinterpreted as newly created resources.

• Manifest Generator:
  • Preserves immutable identity metadata (apiVersion, kind, metadata.name, metadata.namespace, metadata.uid, metadata.creationTimestamp) from the previous revision when processing truncated logs, rather than resetting to an empty reader.
  • Returns the preserved immutable identity reader as ResourceBodyReader on truncated logs (instead of nil), ensuring the truncated log itself retains its immutable identity manifest in the timeline revision and does not appear empty in the UI.
• Nil Revision Handling:
  • Avoids eager empty map initialization at the start of Process(), maintaining prevRevisionReader as nil until a revision is observed, and only extracting identity metadata when a prior revision actually exists.
  • Safely falls back to an empty map node if prevRevisionReader is nil prior to a patch merge.
• Unit & Integration Tests:
  • Added unit tests in TestExtractResourceIdentity verifying field extraction for empty maps, non-identity fields, type-only metadata, full identity metadata, and cluster-scoped resources.
  • Added and updated test cases in TestGroupManifestGenerator verifying that immutable identity metadata is preserved on truncated logs and across single/consecutive truncated logs into subsequent patches, that initial truncated logs merge patches cleanly into empty bodies, and that DeleteOptions after truncated logs return preserved identity readers.

[gemini-code-assist]

Code Review

This pull request modifies the manifest generator task to preserve immutable resource identity metadata (such as apiVersion, kind, name, namespace, uid, and creationTimestamp) when handling truncated logs, rather than completely clearing the previous revision. It introduces a new helper function extractResourceIdentity and adds comprehensive unit tests to verify this behavior. However, a critical compilation error was identified: the variables pathMetadataUID and pathMetadataCreationTimestamp are referenced in the new helper function but are not defined in the global variable block.

[gemini-code-assist]

The variables pathMetadataUID and pathMetadataCreationTimestamp are used in extractResourceIdentity but are not defined in the global var block. This will cause a compilation error. Please define them here.

	pathAPIVersion                = structured.CompileFieldPath("apiVersion")
	pathKind                      = structured.CompileFieldPath("kind")
	pathItems                     = structured.CompileFieldPath("items")
	pathMetadataName              = structured.CompileFieldPath("metadata.name")
	pathMetadataNamespace         = structured.CompileFieldPath("metadata.namespace")
	pathMetadataUID               = structured.CompileFieldPath("metadata.uid")
	pathMetadataCreationTimestamp = structured.CompileFieldPath("metadata.creationTimestamp")

[kyasbal]

Thank you for the review. Both pathMetadataUID and pathMetadataCreationTimestamp are package-level variables defined in resource_helpers.go (lines 30 and 33) within the same package (commonlogk8saudit_impl).

In Go, package-level identifiers are shared across all files within the same package, so they are accessible here without compilation error. Declaring them again in manifest_generator_task.go would cause a Go compilation error (redeclared in this block).