Add Highlight field to SearchHit struct

[tim-holdaway-clever]

Description

For queries specifying highlights, the the SearchHits on the SearchResp now include the highlight information returned in the api response.

Issues Resolved

Closes #653

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[tim-holdaway-clever]

Failing tests

        --- FAIL: TestNodes/Stats/without_request (0.09s)
    --- FAIL: TestSearchTemplate/with_request (0.01s)

appear to also be failing in other recent PRs, for instance in https://github.com/opensearch-project/opensearch-go/actions/runs/12757766943/job/35558719849?pr=652, so seems like are probably not caused by this PR.

Failures look like

        	Error:      	Should be empty, but was [{"op":"remove","path":"/nodes/W0IruYOMTB2U8Ho0B6ZF4w/remote_store"}]

Which seems like maybe the version of OpenSearch cluster that the integration tests are running against may have changed and is now returning some extra unexpected property in the response, or something like that.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.79%. Comparing base (06a6dc8) to head (035de67).
Report is 77 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #654      +/-   ##
==========================================
- Coverage   57.29%   54.79%   -2.50%     
==========================================
  Files         315      374      +59     
  Lines        9823    11035    +1212     
==========================================
+ Hits         5628     6047     +419     
- Misses       2902     3680     +778     
- Partials     1293     1308      +15     

Flag	Coverage Δ
integration	54.79% <ø> (+3.95%)	⬆️
unit	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
opensearchapi/api_nodes-stats.go	100.00% <ø> (ø)
opensearchapi/api_search-template.go	100.00% <ø> (ø)
opensearchapi/api_search.go	100.00% <ø> (ø)

... and 38 files with indirect coverage changes

[dblock]

Which seems like maybe the version of OpenSearch cluster that the integration tests are running against may have changed and is now returning some extra unexpected property in the response, or something like that.

Appreciate it if you could help fix those first, if you have time.

[tim-holdaway-clever]

Appreciate it if you could help fix those first, if you have time.

I can take a look and see if I can reproduce it locally. Integration tests were all passing in my local run using make cluster.build cluster.start && make test-integ race=true, so seems like something in the CI build potentially using against a different version of the cluster or configuration or something, especially since they are failing on other recent PRs.

Do you have any hunches or pointers on where I should look, as I'm not really familiar yet with all the ins-and-outs of this projects testing setup and CI config?

[dblock]

Do you have any hunches or pointers on where I should look, as I'm not really familiar yet with all the ins-and-outs of this projects testing setup and CI config?

I do not. I am mostly just cheerleading in this repo vs. doing real work which is primarily @Jakob3xD and some other contributors more recently :)

[tim-holdaway-clever]

🗒️ Integration tests were failing due to this field that was added to the opensearch 2.18 response. The test was comparing the parsed response to the raw response and failing on the missing field.

[tim-holdaway-clever]

🗒️ Integration tests were failing due to this field that was added to the opensearch 2.18 response. The test was comparing the parsed response to the raw response and failing on the missing field.
See opensearch-project/OpenSearch#15611 for where this was added to 2.18

[tim-holdaway-clever]

🗒️ This ensures that when running integration tests locally, docker isn't using an older cached version of opensearch:latest, and actually gets the most recent one that the CI build will be using.

[dblock]

Thanks for fixing this!