Check prometheus_alerts license in NotifyService
The following discussion from !9830 (merged) should be addressed:
In theory, this enables users without a license to receive notification emails. In practice, this won't happen as those users don't have to ability to configure alerts.
return falseif a user does not have a license for
The NotifyService should check for the presence of the
prometheus_alerts license before performing any actions.
Currently, the NotifyService does not check for a license before sending email notifications and persisting events. It is not possible to setup Prometheus without the license, so there will be no alert notifications without the license. But the NotifyService should anyway check the license.