[FEATURE] Add docvalue_fields to msearch request

[patschl]

Is your feature request related to a problem?

docvalue_fields does not exist for msearch requests in this version of the SDK which currently makes it impossible for us to switch.

What solution would you like?

Add docvalue_fields to the msearch request.

Is there a particular reason this is missing? If not, I will make a contribution.

E: I just realized that quite a few fields are missing, including, but maybe not limited to:

docvalueFields
profile
rescore
version
collapse
indicesBoost
explain
storedFields
timeout
stats

[dblock]

Is there a particular reason this is missing? If not, I will make a contribution.

No, no reason other than it wasn't done.

In general we're trying to add things to https://github.com/opensearch-project/opensearch-api-specification and generate code in clients, see #284 if you are interested in helping!

[dalonlobo]

+1, we are blocked by docvalue_fields too. Requesting to kindly prioritize this feature.