Event-Loop async subscription

[mineiwik]

When one subscribes asynchronously to a custom event using the subscribe_async function, it listens to all events happening on the given event-loop, instead of limiting to the given event(s). I think the problem is that in the subscribe_async implementation, the EspEvent struct is supplied as the generic type for the subscribe call, which by default listens to all events. Shouldn't that use the given D generic that holds the event one has specified?

[mineiwik]

I just tested using the main branch and there it works just fine. It has already been addressed in #466.