Opensearch api support

[tomolopolis]

This is a minimal set of changes to support OpenSearch in working_with_cogstack.

This ideally needs an integration test with an Elastic and an OpenSearch service

[mart-r]

Looks good overall, I'd say.

But this would also need to be implemented for cogstack2.py:
https://github.com/CogStack/working_with_cogstack/blob/main/cogstack2.py

Annoying, I know. But for now, there's 2 different modules for ES/OS stuff.

Furthermore, it would need to be implemented into the cogstac-nlp PR as well:

CogStack/cogstack-nlp#123

[tomolopolis]

starting doing this, but then thought are we going to refactor this anyway, and remove the dupe in due course?

[mart-r]

Yeah, fair enough. Just need to make sure this doesn't slip through the cracks!

[tomolopolis]

I think I can cancel this, as you've replicated the change to cogstack-nlp

[mart-r]

Yes, that's fair. But I'd leave the branch so we can refer to it if/when needed.