Currently, the Aphlict server will crash if invalid JSON data is POSTed to it. I have fixed this to, instead, return a 400. Also made some minor formatting changes.
Ref T4324. Ref T5284. Also, modify the data structure that is passed around (i.e. POSTed to the Aphlict server and broadcast to the Aphlict clients) to include the subscribers. Initially, I figured that we shouldn't expose this information to the clients... however, it is necessary for T4324 that the AphlictMaster is able to route a notification to the appropriate clients.