use _toQuery() when combining queries

[channel-dante]

Is your feature request related to a problem?

The _toQuery() method is often used to combine multiple queries as below.

    builder.query(BoolQuery.of(boolQueryBuilder ->
        boolQueryBuilder
            .must(must.build()._toQuery())
            .filter(should.build()._toQuery())
    )._toQuery());

What solution would you like?

Methods starting with an underscore seem like naming conventions that should only be used internally. Can I continue to use this method as above? If that's the case, could you consider removing the underscore from the method naming like (.toQuery())?

If I am using the method in the wrong way, what is the correct way to combine queries like above?

[dblock]

You're probably using it right. I suggest we deprecate _toQuery() and rename it to toQuery, WDYT? Want to contribute?

[channel-dante]

I'll close it because I understand the intent and the code has been merged(#760) to improve it.