Is there a way to specify part_size for MultipartUploader with Transfer Manager?

[yurguis]

I'm currently using the transfer manager and would like to specify the part_size to be used by MultipartUploader and can't find a way to do it. Is there any way I can achieve this?

[yurguis]

Couldn't find a way to specify part_size without adding the option to the sdk so I have created this PR #3118 where I have added it.

Sample usage:

$uploader = new Transfer($s3Client, $source, $dest, [
   'part_size' => 20971520 // 20MB
]);