When BURP fails to even *start* a backup, it does not trigger a
notification at all. As a result, I may not notice for a few days when
backups are not happening. That was the case this week, when clients'
backups were failing immediately, because of a file permissions issue on
the server. To hopefully avoid missing backups for too long in the
future, I've added two new alerts:
* The *no recent backups* alert fires if there have not been *any* BURP
backups recently. This may also fire, for example, if the BURP
exporter is not working, or if there is something wrong with the BURP
data volume.
* The *missed client backup* alert fires if an active BURP client (i.e.
one that has had at least one backup in the past 90 days) has not been
backed up in the last 24 hours.