Support Session-enabled topics and queues in Arcus.Messaging

[fgheysels]

It is currently not possible to consume a session-enabled topic or queue using Arcus.Messaging.
This is a feature which might not be so often used, but is definitely useful in some scenario's, therefore I think it might be useful to support it.

Unfortunately, this won't be an easy task to do, as the .NET SDK exposes a specific ServiceBusReceiver to consume session-enabled entities: the ServiceBusSessionReceiver class.

I believe that this means that we need to define a new message-pump type in Arcus.Messaging. The thing that makes it difficult, is that it seems that the ServiceBusSessionReceiver is only able to receive messages from one particular session. This means that we would need to have multiple ServiceBusSessionReceiver instances per message-pump. See also here.

I've been looking at how the Azure Function bindings would cope with this, and I've seen that there exists a setting called MaxConcurrentSessions which controls the amount of sessions (ServiceBusSessionReceiver instances?) that can be active at once.

More background info on ServiceBus and sessions can be found here