Stop losing customers at the cancel button.

<script>
  const KEEDR_APP_ID = "kdr_pk_live_...";
  !function(){
    if (window.keedr?.created) return;
    window.keedr = { created: true };
    const s = document.createElement("script");
    s.src = "https://keedr.com/sdk/keedr.js?appId=" + KEEDR_APP_ID;
    s.async = true;
    document.head.appendChild(s);
  }();
</script>

import { createHmac } from "node:crypto";

export async function POST(request: Request) {
  const user = await requireUser(request);
  const sub  = await stripeSubscriptionFor(user);
  const ts   = Math.floor(Date.now() / 1000);

  const message = [APP_ID, sub.customer, sub.id, ts].join(".");
  const authHash = createHmac("sha256", SIGNING_SECRET)
    .update(message).digest("hex");

  return Response.json({ appId: APP_ID, customerId: sub.customer,
    subscriptionId: sub.id, authHash, authTimestamp: ts });
}