Improve upload tool user interface

Right now, the upload tool lets a user select a single file from their computer and upload it. Some ideas for improvement

Require that image to upload is a FITS file (fastest way to do this?)
Ask user if the image already exists in an external archive we support, and suggest they link to that instead (TBD...)
Add required fields for the user uploading the file to fill out, such as a checkbox agreeing the image is theirs or otherwise OK to share publicly, a checkbox agreeing to an appropriate creative commons license, and a valid contact email that won't be shared publicly (what else?)
Handle multiple file uploads gracefully (what is a reasonable upper limit?)
Show a progress bar during the upload process
Display the uploaded image(s) when the upload completes, along with the metadata that will be added to the metadata database, with a note saying they should contact us if anything looks wrong

dirac-institute / trailblazer