Add api for creating pre-signed putobject url

[justinmchase]

Rather than doing the PUT I just need a pre-signed url which I can hand off to a user to do the put for me.

https://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/s3-example-presigned-urls.html#generate-a-pre-signed-url-put

The nodejs aws api has this feature but I'm not exactly sure how to do it here. I don't have a body, I want the user to be able to provide whatever content they want.