Calendar: Use ACKNOWLEDGED VALARM property
Currently evolution-alarm-notify appears and shows reminders for CalDAV events on every device running Evolution, even if they've been dismissed already (or snoozed) on another device. Additionally, when syncing Evolution for the first time with a CalDAV source, evolution-alarm-notify contains shows every single historical reminder for that source.
There is what seems to be a fairly mature IETF draft for standards-based server-side CalDAV VALARM status handling, at https://tools.ietf.org/id/draft-ietf-calext-valarm-extensions-04.html, specifically the "Alarm Acknowledgement" and "Snoozing Alarms" extensions.
It would be great if Evolution could support these (reading from, writing to, and respecting) to avoid having to handle reminders several times, once for each client device.