Use s3_direct_upload with multiple AWS credentials not in config

[donpinkus]

This gem is awesome and I've used it in the past, so thanks for making it!

But now my application lets user's upload files to their own S3 buckets with their own AWS credentials. Unfortunately, in the config for s3_direct_upload, we must set just 1 AWS credential - this obviously stops us from using the gem to let people upload to their own buckets.

Is there a way to override this configuration so any AWS credentials can be passed into s3_direct_upload? If so, it would let this gem power applications that rely on more than 1 AWS credential.

[donpinkus]

SO question: http://stackoverflow.com/questions/23186265/upload-files-directly-to-s3-but-using-arbitrary-aws-credentials