Fixing partial success results for msearch template

[VachaShah]

Description

Same as title

Issues Resolved

Resolves #708

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[reta]

@VachaShah hm I believe status should be always present, we may have an issue on the server side?

[VachaShah]

@reta Yeah I dug through the server side and the server does not return status for msearch template requests. (see additional context section in #708).

[VachaShah]

The server does not set a status for MultiSearchTemplateResponse (https://github.com/opensearch-project/OpenSearch/blob/main/modules/lang-mustache/src/main/java/org/opensearch/script/mustache/MultiSearchTemplateResponse.java#L169) whereas for MultiSearchResponse, it does https://github.com/opensearch-project/OpenSearch/blob/main/server/src/main/java/org/opensearch/action/search/MultiSearchResponse.java#L195.

[VachaShah]

Do you think this is something that should be fixed on the server side? I am not sure if there is any history behind not setting status for mutli search templates 🤔

[reta]

Thanks a lot for digging it in @VachaShah !

Do you think this is something that should be fixed on the server side?

I believe so, the status field should always be set by the server.

[VachaShah]

Got it, thank you @reta! I think we should still merge this fix though so that the users can use it with the current versions of OpenSearch, WDYT?

[reta]

Oh that's right, no objection

[VachaShah]

Thank you! I will raise an issue on OpenSearch to add the status field for multi search templates.

[VachaShah]

@reta I opened an issue on the server for this: opensearch-project/OpenSearch#11133

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-709-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 99bb07a0eefa4e1aededccf016f8b4c3f64e5c3d
# Push it to GitHub
git push --set-upstream origin backport/backport-709-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-709-to-2.x.