Pass kwargs to create_multipart_upload

Hi 👋

We have some kwargs going into create_multipart_upload (using smart_open under the hood, tested with real s3):

kwargs = {'ACL': 'authenticated-read', 'StorageClass': 'STANDARD_IA', 'Metadata': {'summary': 'summary', 'name': 'mypkg', 'version': '1.1'}}
s3.create_multipart_upload(Bucket=..., Key=..., **kwargs)

Can this currently be mocked? It looks like the mocked method does not take any CamelCase arguments 🤔

Currently, these kwargs seem to be ignored, as they go missing in a round trip.

[ddelange]

Yup, test was passing an empty BytesIO() to smart_open. Adding some bytes solved StorageClass showing up 👍

[ddelange]

Many thanks! Looking into StorageClass going missing, most likely not on your side.