* [bugfix] add Date and Message-ID headers for email
This should make spam filters more happy, as most of them grant some
negative score for not having those headers. Also the Date is convenient
for the user receiving the mail.
* make golangci-lint happy
* start fiddling about with email sending to allow multiple recipients
* do some fiddling
* notifs working
* notify on closed report
* finishing up
* envparsing
* use strings.ContainsAny
