Warning when no new photos have been available for X days or invocations

[kjoconnor]

Summary

Using the same SMTP notification for auth issues, we can notify via SMTP when no new photos have been available to download for X number of days.

Context

In case iCloud Photo backups are not working on the device (out of storage, iCloud auth issues, etc) it would be nice to have icloudpd be able to warn you if your photos are not being synced to iCloud properly.

[AndreyNikiforov]

IIUC you want an alert/notification when new assets are present on icloud.com, but were not downloaded. What are the cases of assets not being downloaded and not marked by special reaction from icloudpd? Both examples provided (out of storage and auth issues) already have special "handling" - terminate icloud with error. Any notification/alerting can be built on top of that using external apps/services.