title: Generate expiring download link for newly purchased item
body: <p>I am building a simple static website selling a single pdf file using the Stripe checkout api.</p>
  <p>I would like to be able to generate an expiring download link after the customer successfully purchased the pdf.</p>
  <p>I am really not sure about how to do this, but I was thinking about using firebase to store the file in a bucket and somehow use a cloud function to generate a temporary download link that expires after some time, but I am not sure how to go about this (or if this is even the best solution).</p>
  <p>Can anyone give me some help about which direction to go here?</p>