[feature] Add support for Client Side Encryption

[frittentheke]

I'd like to propose adding the ability to transparently apply encryption to the objects uploaded to the external S3 service.
Depending on the client library / SDK this is easier said than done on the actual client:

• AWS Boto3 Add Client Side Encryption to S3 client boto/boto3#3395
  • See comment regarding the state of Golang: Add Client Side Encryption to S3 client boto/boto3#3395 (comment)
• MinIO [feature request] Support for Client Side Encryption minio/minio-py#1232

and I'd like to think that having the encryption managed, applied and ensured at the Chorus-level is what's suitable for quite a few environments that simply don't want to trust their data to the SSE (Server Side Encryption) mechanisms of an external S3 provider.