class ActiveStorage::RepresentationsController

authenticated redirection controller.
security-through-obscurity factor of the signed blob and variation reference, you’ll need to implement your own
Note: These URLs are publicly accessible. If you need to enforce access protection beyond the
Take a signed permanent reference for a blob representation and turn it into an expiring service URL for download.

def show 

def show
  expires_in ActiveStorage.service_urls_expire_in
  redirect_to @blob.representation(params[:variation_key]).processed.service_url(disposition: params[:disposition])
end