Filtering of events based on channel

[lulf]

One common pattern for drogue iot operators is to use the same mechanism as applications for communicating with devices/gateways on the 'other side'. Using channels, one can multiplex a given application or topic to communicate within separate 'domains', like 'dfu', 'btmesh' or 'devices'.

However, at present applications are required to do all the filtering of the events: parsing the payload as cloud events messages, inspect the message, look at the 'subject' and dispatch/ignore accordingly. Having a more native way to express this such as using mqtt topic hierarchy or the ability to route events for a specific channel to another topic could be a useful addition to reduce application logic overhead.