Optional DIDComm messaque queuing #2299
Description
From #2292:
Should we take into account an agent that does not want to queue? Can we disable it instead of using in memory (which could be a memory leak)
Currently, Queue Transport Repository is optional and, if not defined, will default to an in-memory one. This can probably be useful in demos and testing (e.g. a dev mediator), and maybe a few edge cases like a mobile agent that interacts with an IoT device, but it is not common and I think it makes sense to not queue at all when a queueTransportRepository is not defined in the DIDComm module config.