More email notification triggers

[Lanhild]

As a sysadmin, I'd like to be able to receive email notifications when an app with automatic updates disabled requires a manual update.

[girish]

We have a notification type already for this but no email is sent. I think it was not implemented because we possibly have to aggregate all the manual updates into a single email? Like if you had 10 WP instances, are you expecting 10 mails or a single mail?

[Lanhild]

@girish great question. I think an email aggregating updates per app would be fitting

[girish]

@Lanhild of course, the instances of the same app could all be on different versions.

[Lanhild]

@girish IMO, the version information wouldn't matter for a notification email. I'd just like to know when a manual updates required