Angular flash success

This is back when I was looking at serializing out action / controller in the response (we don't need to, and it's hard)

But this is a pretty clear-cut improvement, I think. We're telling the serializer directly about the event it has to serialize, if there is one, which gets rid of all of the guesswork around 'what kind of eventable does this event have?' in the event serializer. Much recommend.