More javadocs

[ker2x]

Friendly greetings !

i wrote more javadoc and fixed some mistake from the previous PR.
I ran gradle precommit and check

There are some errors unrelated to my commits

meta ticket #221

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.

[github-actions]

Compatibility status:

Checks if related components are compatible with change 9eda6a9

Incompatible components

Skipped components

Compatible components

[ker2x]

i switched laptop and forgot the signoff on some commits 😢

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/25313/
• CommitID: 9eda6a9
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[reta]

i switched laptop and forgot the signoff on some commits 😢

I think you could rebase with --signoff (or rebase + squash with --signoff)

[ker2x]

i close this PR and try to fix this with a squash/merge