POC/Spike for Push notification Metrics

Inside of the sender classes that speak with the 3rd party system, we need to "log" the results to a kafka topic.

For instance, on iOS push, this method/callback would be good to log info if a token was accepted by APNs, or not:
https://github.com/aerogear/aerogear-unifiedpush-server/blob/0725d0b7a90e191e8aba8aed7dd8ad07d45e0930/push/sender/src/main/java/org/jboss/aerogear/unifiedpush/message/sender/apns/PushyApnsSender.java#L130-L147

More to be defined