Document signal detection for replication

[johanandren]

When we worked on akka-edge-rs we discussed scenarios where it is useful to more or less dynamically trigger a more fine grained replication of events. A device collects fine grained events, but normally replicates only some aggregate or some of the events to keep the stream of events to the edge/cloud manageable, however when some specific event happens, an error, or maybe a support case, it is interesting to replicate and look at a more fine grained recent history for a particular device.

I think we have ideas about how this could be achieved (for example local history queue in entity, specific command triggers writing that history as one or more special events for replication) but we never ended up mentioning it in the edge-rs docs.

Could potentially be interesting also for the Akka Edge use cases, for the same reason.