feat: Make resource lookup case-insensitive to match Kubernetes API behavior

[Kevinz857]

Make Resource Lookup Case-Insensitive to Match Kubernetes API Behavior

What type of PR is this?

/kind feature
/kind bug

What this PR does / why we need it

This PR implements case-insensitive resource lookup in the dynamic client to match the actual behavior of the Kubernetes API. Currently, when using the dynamic client to look up resources, the search is case-sensitive, which causes issues when users attempt to look up resources with different casing than what's defined in the API server.

The Kubernetes API itself is case-insensitive when it comes to resource kinds. For example, both kubectl get pod and kubectl get Pod work correctly. This PR makes the Python client's behavior consistent with the API server's behavior.

Key changes

• Added a _find_resource_case_insensitive method to the Discoverer class
• Modified the search methods in both LazyDiscoverer and EagerDiscoverer classes to:
  • First try exact case matching (original behavior)
  • If no match is found and a kind is specified, attempt case-insensitive lookup
  • On failure, refresh the cache and retry both strategies
• Added test cases to verify case-insensitive lookup functionality

Special notes for your reviewer

This change is backward compatible with existing code as it maintains the same behavior for exact case matches. It only adds the additional capability to find resources when the case doesn't exactly match.

Does this PR introduce a user-facing change?

Make resource lookup case-insensitive in the dynamic client to match Kubernetes API behavior

Which issue(s) this PR fixes:

Fixes #2402

[k8s-ci-robot]

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This pull-request has been approved by: Kevinz857
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[roycaihw]

/assign @fabianvf

[roycaihw]

The Kubernetes API itself is case-insensitive when it comes to resource kinds. For example, both kubectl get pod and kubectl get Pod work correctly. This PR makes the Python client's behavior consistent with the API server's behavior.

I think the case-insensitive behavior comes from kubectl. Kubernetes API server is case sensitive. One can verify that by running kubectl with --v=9 to check the actual API request.

IIRC other clients like client-go are also case-sensitive.

/priority awaiting-more-evidence