Creating API objects from JSON data

Is your feature request related to a problem?

It is currently not possible to create API objects from JSON data.

What solution would you like?

For example we would like to do something like code below:

InputStream input = this.getClass()
    .getResourceAsStream("some-index.json"); 

CreateIndexRequest req = CreateIndexRequest.of(b -> b
    .index("some-index")
    .withJson(input) 
);

boolean created = client.indices().create(req).acknowledged();

What alternatives have you considered?

This withJson() method is currently supported on all API objects of the elasticsearch java client, and after moving to opensearch we feel this enhancement is greatly needed in opensearch java client too.

Start by tracing the CreateIndexRequest and client.indices().create entry points shown in the example, then compare how JSON input is handled by the existing API objects. Implement the requested withJson() behavior for API objects and verify that the example can create an index from some-index.json.