[FEATURE] Add a collapse method to opensearchpy.helpers.search.Search

[qcoumes]

Is your feature request related to a problem?

The only way to currently add a collapse requirement to a search body is to use the extra() method. This is not the cleanest way because as mentioned in its docstring, extra() is mostly here for backward compatibility.

What solution would you like?

A solution would be to treat it the same way as sort:

• Add a collapse() method opensearchpy.helpers.search.Search which creates and stores the dict in a self._collapse attribute.
• Add self._collapse, if defined, in the body of the request in the to_dict() method.

[wbeckler]

I can't see anything of this sort, but just in case I'm missing something, I'll ask: can you think of any case, in which this is implemented, in which we would inadvertently break someone's working code?

[qcoumes]

I think the addition of a method and a "private" attribute on Search should not break anybody's working code.

[wbeckler]

okay, let's do it! @qcoumes if you want to take a crack at it, go for it.

[qcoumes]

I opened a PR: #409

[qcoumes]

Completed in #409

[CorneeSean]

Hello,
we just switched to AsyncOpenSearch and it seems that AsyncSearch lacks collapse feature altogether:
https://github.com/opensearch-project/opensearch-py/blob/main/opensearchpy/_async/helpers/search.py

[dblock]

I reopened #769.