[Extensions] Moving ExtensionsRequest to use Protobuf

[saratvemulapalli]

Description

As part of opensearch-project/opensearch-sdk-java#337. Moving the first API to protobuf to have seamless version support.

Issues Resolved

Part of #opensearch-project/opensearch-sdk-java#642
Also first introduction of protobuf #6844

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/13341/
• CommitID: f1940e0
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/13343/
• CommitID: 49a937a
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/13339/
• CommitID: 4b4c9e2
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[saratvemulapalli]

@reta @owaiskazi19 @peternied @VachaShah sorry couldn't get back to this since a week. The change is now ready for review. Everything works :)

[reta]

👍

[reta]

👍

[reta]

Nice one @saratvemulapalli , pretty clean and simple

[owaiskazi19]

Overall LGTM! Thanks for addressing the feedback @saratvemulapalli! Do you think we should add tests for the generated Protobuf classes?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.indices.replication.SegmentReplicationIT.testScrollWithOngoingSegmentReplication

• URL: https://build.ci.opensearch.org/job/gradle-check/14392/
• CommitID: 84019a7
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.indices.replication.SegmentReplicationIT.testScrollCreatedOnReplica
      1 org.opensearch.cluster.allocation.AwarenessAllocationIT.testThreeZoneOneReplicaWithForceZoneValueAndLoadAwareness

• URL: https://build.ci.opensearch.org/job/gradle-check/14393/
• CommitID: b71ec29
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/14394/
• CommitID: 33e500a
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[saratvemulapalli]

Overall LGTM! Thanks for addressing the feedback @saratvemulapalli! Do you think we should add tests for the generated Protobuf classes?

Tests for generated classes, I am like "protoc" can you generate unit tests too :D.
Anyway for generated code its already concise and optimized, no point writing tests for message data types/for internal protobuf business logic.
@reta WDYT ?

[saratvemulapalli]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/14394/
• CommitID: 33e500a
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

Looks like 2.7 is on its way, i'll rebase my PR.

 [2.6.1] build complete, generating: /var/jenkins/workspace/gradle-check/search/distribution/bwc/bugfix/build/bwc/checkout-2.6/build/14394.tar.bz2
 [2.6.1] 
 [2.6.1] BUILD SUCCESSFUL in 5m 9s
 [2.6.1] 165 actionable tasks: 165 executed

> Task :distribution:bwc:minor:buildBwcLinuxTar
 [2.8.0] > Task :distribution:archives:buildLinuxTar
 [2.8.0] > Task :distribution:archives:linux-tar:assemble
 [2.8.0] build complete, generating: /var/jenkins/workspace/gradle-check/search/distribution/bwc/minor/build/bwc/checkout-2.x/build/14394.tar.bz2

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/14395/
• CommitID: 1089388

[VachaShah]

This looks great!

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-6960-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c0f7c192baa574407d9d081343fd6318c092cbc5
# Push it to GitHub
git push --set-upstream origin backport/backport-6960-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-6960-to-2.x.