[Feature Request] Support `BucketKeyEnabled` for upload_file

[jed326]

Was wondering if there are any technical limitations for supporting the BucketKeyEnabled argument on upload_file? It is already supported by put_object and the multi-part upload APIs, which I would assume upload_file calls under the hood.

It is mentioned in this blog: https://aws.amazon.com/blogs/storage/reduce-encryption-costs-by-using-amazon-s3-bucket-keys-on-existing-objects/ that BucketKeyEnabled is not supported. Based on the patch in the repository mentioned in that blog, it looks like a one liner change: https://github.com/simon-data/s3transfer/commit/02eb942a5655af52abe07fcf2977e80eb49dec91

So wanted to know if there was any reason why this never got pulled into the official release?