> Done. Added the payload to the put request

I'm not sure this is what @andrewgaul meant? If I understood his comment correctly, he meant "create the PUT request *without* supplying blob2, then attach the input to the request".

This would capture the intended case where a user asks the server for a pre-signed request (in which case the server does _not_ have the blob to attach), then attaches the payload before uploading.

@andrewgaul Thoughts?