We are a few versions behind on this gem. We need to update it for S3 multipart uploads. In the current version we are using, we cannot do this:
Discourse.store.s3_helper.object(key).presigned_url(:upload_part, part_number: 1, upload_id: multipart_upload_id)
The S3 client raises an error, saying the operation is undefined. Once I updated the gem this operation works as expected and returns a presigned URL for the upload_part operation.