[1.3] Fix Door Lock cluster to not repond DUPLICATE when there is no duplication of credentials.

[bzbarsky-apple]

Spec issue tracking the spec not being clear:
https://github.com/CHIP-Specifications/connectedhomeip-spec/issues/11707

Cherry-pick of #39254

Testing

YAML test added.

[gemini-code-assist]

Code Review

This pull request addresses an issue in the Door Lock cluster where setting a credential to its existing value would incorrectly result in a DUPLICATE response. The fix in door-lock-server.cpp correctly modifies the duplicate check logic to ignore the credential slot being operated on, which resolves the issue. The added YAML test case in DL_UsersAndCredentials.yaml specifically verifies this scenario, ensuring that modifying a credential to its current value is now allowed and returns a success status.

The changes are well-targeted, and the code is clear. The accompanying comments and test case enhance understanding and maintainability. Overall, this is a good fix that improves the correctness of the credential management logic.

Summary of Findings

• Code Correctness: The modification in door-lock-server.cpp correctly adjusts the duplicate credential check to ensure that setting a credential to its existing value does not trigger a DUPLICATE error. This aligns with the intended behavior described in the associated spec issue.
• Testing: The new YAML test case in DL_UsersAndCredentials.yaml effectively validates the fix by attempting to modify a credential to its current value and expecting a successful outcome. This is a valuable addition for regression prevention.
• Clarity and Maintainability: The code changes are minimal and easy to understand. The comment added in the C++ code provides excellent context regarding the spec ambiguity and the rationale for the change.

Merge Readiness

The changes in this pull request appear to be correct and well-tested for the specific issue they address. The code is clear and follows existing patterns. While I cannot approve the pull request myself, based on this review, the changes seem ready for merging pending successful CI checks and any other necessary reviews. No critical or high-severity issues were found in the changed code.