[OSGeo] #3452: Add a null-mailer role for send-only mail infrastructure (for cron)

#3452: Add a null-mailer role for send-only mail infrastructure (for cron)
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Reporter: strk | Owner: strk
     Type: task | Status: new
Priority: normal | Milestone: Unplanned
Component: SysAdmin/Ansible | Keywords:
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Some of our system services need to send email to report issues (at least
"cron" does) so it's useful to have the ability to determine how that mail
sending is done.

At the moment when you install "cron" package on Debian you get EXIM mail
server as a dependency, and I didn't check HOW it is configured.

Chances are (but I didn't verify) that any mail server would satisfy the
Debian packaging dependency and in that case we can configure our own.

An experiment with "nullmailer" package was pushed as a PR but it needs
more thinking, so here's a ticket.

The WIP PR: Making sure you're not a bot!
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Ticket URL: <Making sure you're not a bot!;
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