feat: add fields - raftAppliedIndex , errorsList, dbSizeInUse and isLearner in StatusResponse

[mahanteshwar-git]

What this PR does

This PR adds support for retrieving additional fields in StatusResponse

• raftAppliedIndex
• errorsList
• dbSizeInUse
• isLearner

Why this is useful

AppliedRaftIndex in comparison with RaftIndex can be used to determine if the PromoteMember operation could be retried
isLearner call in StatusResponse removes the need for another call to MemberList to determine if the member is a learner

Implementation Details

• Added a fields to the class: StatusResponse
• Updated testMemberStatus to verify that the new fields are indeed present and populated

Related Issues / Discussions

This change was based on discussion in #1499

---

Checklist

• Code compiles successfully
• Tests added / updated
• Documentation updated (if needed)
• Ready for review

---

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mahanteshwar-git
Once this PR has been reviewed and has the lgtm label, please assign vorburger for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[mahanteshwar-git]

Hi @lburgazzoli , @fanminshi , @vorburger ,

Please review the pull request

[Copilot]

Pull Request Overview

This PR adds support for retrieving additional metadata fields in the etcd StatusResponse including raft applied index, error list, database size in use, and learner status. These fields enable better monitoring and decision-making for etcd cluster operations.

Key changes:

• Added four new fields to the StatusResponse protobuf definition
• Exposed these fields through getter methods in the Java StatusResponse class
• Added comprehensive test coverage to verify the new fields are populated correctly

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
jetcd-grpc/src/main/proto/rpc.proto	Added four new fields to StatusResponse message definition
jetcd-core/src/main/proto/rpc.proto	Duplicate addition of the same four fields to StatusResponse
jetcd-core/src/main/java/io/etcd/jetcd/maintenance/StatusResponse.java	Added getter methods for the new fields with proper documentation
jetcd-core/src/test/java/io/etcd/jetcd/impl/MaintenanceTest.java	Enhanced test to verify new fields are present and have expected values

Comments suppressed due to low confidence (2)

jetcd-core/src/main/java/io/etcd/jetcd/maintenance/StatusResponse.java:111

• The method name 'getIsLearner()' is not conventional for a boolean getter. It should be 'isLearner()' to follow standard Java naming conventions for boolean getters.

    public boolean getIsLearner() {

jetcd-core/src/test/java/io/etcd/jetcd/impl/MaintenanceTest.java:83

• The test only verifies that the error list is empty, but doesn't test the case where errors might be present. Consider adding a test case that verifies the behavior when errors are actually returned.

        assertThat(statusResponse.getErrorList().size()).isEqualTo(0);