[Rule-based Auto-tagging] Modify get rule api to suit nested attributes

[ruai0511]

Description

This PR enhances the _rules/workload_group GET API to support filtering by nested attributes in addition to top-level fields. Previously, users could filter only by top-level attributes, such as index_pattern. With this update, the API now supports filtering on nested attributes like principal.username and principal.role.

Examples

Previously it supports:

GET _rules/workload_group?index_pattern=my-index

Returns all rules with index_pattern matching the prefix my-index.

Now it also supports nested attribute filter:

GET _rules/workload_group?principal.username=admin&principal.role=a

Returns all rules where principal.username equals admin and principal.role equals a.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

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 7a51365: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

❌ Patch coverage is 86.11111% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.95%. Comparing base (2817029) to head (b076cea).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...ule/service/IndexStoredRulePersistenceService.java	33.33%	3 Missing and 1 partial ⚠️
...search/rule/storage/IndexBasedRuleQueryMapper.java	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #19429      +/-   ##
============================================
- Coverage     73.00%   72.95%   -0.05%     
+ Complexity    70373    70337      -36     
============================================
  Files          5708     5708              
  Lines        322433   322460      +27     
  Branches      46695    46702       +7     
============================================
- Hits         235385   235258     -127     
- Misses        68066    68216     +150     
- Partials      18982    18986       +4     

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[github-actions]

❌ Gradle check result for e99f7bd: FAILURE

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[github-actions]

❌ Gradle check result for 8e8d45b: FAILURE

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[github-actions]

❕ Gradle check result for b076cea: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.