[FEATURE] Add ml-commons APIs in the OpenSearchClient

[Zhangxunmt]

Is your feature request related to a problem?
When integrating ml-commons in other Java applications like data prepper, lambda, etc, it's better to use the SDSK client to interact with ml-commons. Hence, we should include ml-commons APIs in the OpenSearch Client. https://opensearch.org/docs/latest/clients/java/.

What solution would you like?
Include the ml-commons APIs in the Java Client as the default offering.

What alternatives have you considered?
We already have ml-commons in the OpenSearch-Py, but that's only for python applications.

Do you have any additional context?

[ylwu-amzn]

@nathaliellenaa I think we can use API spec to generate Java client code. Can you confirm ?

[nathaliellenaa]

Yes, we can use API spec to generate Java client code. This is the YAML file for generating the code from spec in opensearch-java and we can see in this PR that the ML APIs are generated in the Java client code.

[Zhangxunmt]

@nathaliellenaa sounds good! If we can make this client generated and released in the next version, the first user of this java ml-commons client will be data prepper.

[nathaliellenaa]

Sure @Zhangxunmt, I'll make sure all ML APIs are released in the next version.

[pyek-bot]

@Zhangxunmt let's assign this to @nathaliellenaa ?