akka.stream.alpakka.s3.headers
Documentation: http://docs.aws.amazon.com/AmazonS3/latest/dev/ServerSideEncryptionCustomerKeys.html
base64-encoded encryption key for Amazon S3 to use to encrypt or decrypt your data.
optional base64-encoded 128-bit MD5 digest of the encryption key according to RFC 1321.
Documentation: http://docs.aws.amazon.com/AmazonS3/latest/dev/ServerSideEncryptionCustomerKeys.html