Add aggregation support

[obukhow]

Add aggregation support for queries

An aggregation summarizes your data as metrics, statistics, or other analytics.
https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations.html

Description

Started by implementing two most common used aggregations – terms bucket and stats metric aggregation.
Other aggregations type could be implemented by extending AggregationInterface

• Bug fix
• Feature addition
• Code refactoring
• Documentation update
• Other (please explain):

Related Issue

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual testing

Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my code.
• I have made corresponding changes to the documentation.
• I have added tests that ensure my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published in downstream modules.

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All modified and coverable lines are covered by tests ✅

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Files with missing lines	Coverage Δ
effdsl.go	69.30% <100.00%> (+3.00%)	⬆️
search_aggregation.go	100.00% <100.00%> (ø)

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[sdqri]

Thanks for the contribution. Aggregation support has since been implemented across metrics, bucket, and pipeline aggregations in v2.7.0, along with updated docs and tests. I’m closing this PR as it’s now superseded by the merged changes.