Adding ChecksumAlgorithm option to AVAILABLE_OPTIONS
Adding ChecksumAlgorithm option to AVAILABLE_OPTIONS

This options enables S3 to compute the desired checksum without the need to download the file. Here is some doc links:
https://docs.aws.amazon.com/aws-sdk-php/v3/api/api-s3-2006-03-01.html#putobject
https://docs.aws.amazon.com/AmazonS3/latest/userguide/checking-object-integrity.html#large-object-checksums
thephpleague/flysystem-aws-s3-v3