[FEATURE] OpenSearch java doc tags

[saratvemulapalli]

Adding up to the conventions, opening this issue to discuss java doc tags.
We use:

• opensearch.internal
• opensearch.api
• etc
  Lets chat and clean up the code base for feature/extensions and SDK with clear communication about which tag to be used at what times.

[dbwiddis]

My 2c:

clean up the code base for feature/extensions

This will be eventually merged to main, so we should simply follow the OpenSearch policy there. Yes, we should clean things up and use this issue to ask any questions.

and SDK

There's no requirement that we use exactly the same convention and I'd rather not. I'm a big fan of package-based API. It's very simple:

• If the class is in org.opensearch.sdk package, it's API. Otherwise it's internal.

If we want another api package, we can add one.

This aligns with the vision of JPMS, where there is package-level control over what other modules can use. Mixing API classes in packages with non-API stuff forces us to open the whole non-API package in a module.

[dbwiddis]

Hey @saratvemulapalli what do you think we need to do to complete this? My thoughts:

1. inventory all the classes
2. categorize them as "definitely API" or "definitely internal" or leave blank
3. engage in a spirited discussion on this issue on the blank ones
4. assign someone this issue to add the annotation (OpenSearch feature/extensions side) or put in the right package (SDK side).