Fix: Update field names in /index/_recovery API response to snake_case for consistency

[Aradhya2708]

Description

This PR updates field names in the SnapshotRecoverySource response to follow snake_case, ensuring consistency across OpenSearch API responses. Specifically, it modifies the following fields:

• isSearchableSnapshot -> is_searchable_snapshot
• remoteStoreIndexShallowCopy -> remote_store_index_shallow_copy
• sourceRemoteStoreRepository -> source_remote_store_repository
• sourceRemoteTranslogRepository -> source_remote_translog_repository

This update aligns the naming conventions within the API, addressing an inconsistency in the /{index}/_recovery API response format.

Related Issues

Resolves #16334

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

✅ Gradle check result for aa9aeda: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 72.10%. Comparing base (0363aa7) to head (aa9aeda).
Report is 59 commits behind head on main.

Files with missing lines	Patch %	Lines
...org/opensearch/cluster/routing/RecoverySource.java	0.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #16541      +/-   ##
============================================
+ Coverage     72.00%   72.10%   +0.10%     
- Complexity    65038    65080      +42     
============================================
  Files          5313     5313              
  Lines        303454   303454              
  Branches      43910    43910              
============================================
+ Hits         218510   218819     +309     
+ Misses        67040    66696     -344     
- Partials      17904    17939      +35     

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[dbwiddis]

Thanks for this fix, @Aradhya2708 ! A few things:

1. Please add a CHANGELOG entry for this, in the "unreleased 3.0" section since it will not be backported.
2. You'll need to update the spec at https://github.com/opensearch-project/opensearch-api-specification/blob/main/spec/schemas/indices.recovery.yaml for the 3.0 tests

[dbwiddis]

Should this one also be changed?

[owaiskazi19]

@dbwiddis we might need BWC tests for this change?

[dbwiddis]

@dbwiddis we might need BWC tests for this change?

It is by definition not backwards compatible. This is a 3.x-only change. It needs to be documented.

[msfroh]

1. Please add a CHANGELOG entry for this, in the "unreleased 3.0" section since it will not be backported.

Note that you'll need to add the entry in https://github.com/opensearch-project/OpenSearch/blob/main/CHANGELOG-3.0.md.

(We split the 2.x and 3.0 changelogs a few months ago.)

[opensearch-trigger-bot]

This PR is stalled because it has been open for 30 days with no activity.

[dblock]

Thanks @Aradhya2708!

• This path doesn't seem to be covered by tests, it should, even if trivial.
• Is there a way to add something to CI that prevents this problem in the future? Maybe tests that retrieve data inherit from a class that always checks for this type of thing?