Additional logging / metrics

[bmonkman]

Add logging of individual actions (sent email to user, etc.) - potentially with obfuscation of addresses?
Add metrics using the go prometheus client: https://prometheus.io/docs/guides/go-application/

[bmonkman]

I'm also seeing some issues with fluentd parsing some of these logs. Stuff like level should be moved under log: https://www.elastic.co/guide/en/ecs/master/ecs-log.html