listLayers API should return empty list instead of 400 when no layers exist

[shekhar316]

Describe the bug
Currently, when calling the listLayers, listMetadataProfiles, listMetricProfiles API and no layers exist, the API responds with a 400 Bad Request.

Why this is problematic:

• Unexpected error handling: Returning a 400 requires clients to handle an exception even when the request is technically valid. “No layers exist” is not an error, it is a legitimate state.
• API design best practices: RESTful API design generally treats “no data” as a valid response, not an error. Returning an empty array is the standard approach for list endpoints.

Expected behavior

• Update APIs to return [] (empty list) when no layers exist.
• Ensure the response code is 200 OK to indicate a successful request.

Relevant logs

{
  "message": "No layers found!",
  "httpcode": 400,
  "documentationLink": "",
  "status": "ERROR"
}

[github-actions]

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