async-aws-s3 adapter - send pre-calculated checksum

[Nickolaus]

Feature Request

Q	A
Flysystem Version	3.23.0
Adapter Name	async-aws-s3 adapter
Adapter version	3.22.0

Scenario / Use-case

The async-aws-s3 adapter should, be able to send a pre-calculated checksum during upload.
See:
https://docs.aws.amazon.com/sdk-for-php/v3/developer-guide/s3-checksums.html

I have already tried this for SHA1 by adding ChecksumSHA1 to AVAILABLE_OPTIONS in the AsyncAwsS3Adapter and then invoke write with the following config:
['ChecksumSHA1' => base64_encode(sha1($content))]

According to aws docs this should work however it throws the following exception:
Value for x-amz-checksum-sha1 header is invalid.

Also tried without base64_encode but the result is the same.

It would be awesome if this feature could be supported, I would have created a PR but as stated above I (currently) cannot get it to work in the first place

Summary

Send pre-calculated checksum using async-aws-s3 adapter on writing to storage.