If we add an endpoint that reports the last export time and returns an error if it was more than x minutes ago, we can point uptimerobot to this instead of the homepage and get reports when ebook generation fails (as happened this morning when the disk filled up but the web server was still fine and so the homepage didn't shown an error). The last export time is stored in the database.
- New end point at e.g. /uptime that returns a 5xx error when the last export was more than 15 minutes ago
- Change the uptimerobot settings to point to this