Adding a guide for making raw json requests using the client

[VachaShah]

Description

Same as title

Issues Resolved

Closes #395

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[VachaShah]

This code is tested against OpenSearch cluster.

[dblock]

LGTM. Can we add a runnable sample along with this?

[Jakob3xD]

Can we add a runnable sample along with this?

Not 100% sure what you mean with that.
I updated the code blocks in such a way that if you copy them in the same order you will get a working go file. Similar to the other guids. See the main() function and the started exaple() function in the Setup section. Which I btw. forgot to add to the list on the top.

[dblock]

We had a lot of contributions where code didn't work when copy-pasted, so in other clients we started adding samples that users can "just run", e.g. https://github.com/opensearch-project/opensearch-py/tree/main/samples. WDYT?

[codecov]

Codecov Report

Merging #399 (2e78c3d) into main (81200d8) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

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  Lines        9820     9820           
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  Misses       2904     2904           
  Partials     1294     1294           

Flag	Coverage Δ
integration	50.82% <ø> (ø)
unit	12.82% <ø> (ø)

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[Jakob3xD]

Added samples for all guids, as I already had them when I updated the guids.

Once this is merge we could replace the code blocks of the guids with permanent links to the files instead of copy paste the code?

[dblock]

Once this is merge we could replace the code blocks of the guids with permanent links to the files instead of copy paste the code?

You could, but other clients don't really do that. I see guides kept to something concise and copy-pasted and working samples. Ideally samples should be compiled and run as integration tests and guide reference code, of course, but that needs tools.

[dblock]

We forgot to link json.md from USER_GUIDE. Maybe in a future PR?