Code review comment for lp://staging/~larsu/indicator-messages/add-simple-dbus-api

A nice to have that I just realised is missing is a (public) signal for when the notification is dismissed by swiping left or tapping "Clear All". I can see the Dismiss on dbus, fwiw:

method call sender=:1.36 -> dest=:1.70 serial=279 path=/com/canonical/indicator/messages/ubuntu_system_settings_desktop; interface=com.canonical.indicator.messages.application; member=Dismiss
   array [
   ]
   array [
      string "msg-id"
   ]