Adds the Fields field containing the document fields to the SearchHit struct

[thekogo]

Description

Add fields fields in SearchHit for support mapping response with fields key

Issues Resolved

For support retrieve specific fields in the search response
Request

{
  "query": {
    "match": {
      "username": "thekogo"
    }
  },
  "fields": [
    "username",
    "email"
  ],
  "_source": false
}

Response (add mapping for support this response)

{
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "index-001",
        "_id" : "0",
        "_score" : 1.0,
        "fields" : {
          "username" : [
            "thekogo"
          ],
          "email" : [
            "admin@gmail.com"
          ]
        }
      }
    ]
  }
}

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 57.29%. Comparing base (392013b) to head (7fa967d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #508   +/-   ##
=======================================
  Coverage   57.29%   57.29%           
=======================================
  Files         315      315           
  Lines        9823     9823           
=======================================
  Hits         5628     5628           
  Misses       2902     2902           
  Partials     1293     1293           

Flag	Coverage Δ
integration	50.83% <ø> (ø)
unit	12.84% <ø> (ø)

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

Files	Coverage Δ
opensearchapi/api_search.go	100.00% <ø> (ø)

[VachaShah]

Thank you @thekogo for your contribution!

A few comments:

1. Could we also add a test for the new field? https://github.com/opensearch-project/opensearch-go/blob/main/opensearchapi/api_search_test.go
2. Please add a CHANGELOG entry.

[VachaShah]

Can you please signoff your commits? You can amend your commits using `git commit --amend -s" to sign them off. https://github.com/opensearch-project/opensearch-go/blob/main/CONTRIBUTING.md#developer-certificate-of-origin

[thekogo]

Sorry I'm not sure why Lint check / Prettify (pull_request) error with

Run npm i -g npm@8 && npm i -g prettier
npm ERR! code EACCES
npm ERR! syscall mkdir
npm ERR! path /usr/local/share/man/man5
npm ERR! errno -13
npm ERR! Error: EACCES: permission denied, mkdir '/usr/local/share/man/man5'
npm ERR!  [Error: EACCES: permission denied, mkdir '/usr/local/share/man/man5'] {
npm ERR!   errno: -13,
npm ERR!   code: 'EACCES',
npm ERR!   syscall: 'mkdir',
npm ERR!   path: '/usr/local/share/man/man5'
npm ERR! }
npm ERR! 
npm ERR! The operation was rejected by your operating system.
npm ERR! It is likely you do not have the permissions to access this file as the current user
npm ERR! 
npm ERR! If you believe this might be a permissions issue, please double-check the
npm ERR! permissions of the file and its containing directories, or try running
npm ERR! the command again as root/Administrator.

npm ERR! A complete log of this run can be found in: /home/runner/.npm/_logs/2024-04-04T18_42_12_[7](https://github.com/opensearch-project/opensearch-go/actions/runs/8559713019/job/23457055244?pr=508#step:3:8)53Z-debug-0.log
Error: Process completed with exit code 243.

[VachaShah]

Was able to get a clean run for prettify. Looks like some intermittent issue.