Slower subscribers can block the event protocol handler

[daviddawson]

Muon Version: 7.1.6 Language: clojure Services in Use: Photon

Subscriber buffer is open to being overloaded when the RS protocol is running slower than the event ingestion. When it overloads, event protocol will still persist in all cases, however the window buffer will begin to drop messages for the slow subscribers.

This should be fixed by adding a persistence mechanism to allow larger buffering to take slow subscribers into account.