Is your feature improvement request related to a problem? Please describe.
Debugging a Cumulocity core issue with thin-edge recently has led me to see how useful the existing mosquitto logs are for explaining what is going on with MQTT communication (with the correct settings in mosquitto, cat /var/log/mosquitto/mosquitto.log | grep Cumulocity will show all the packets sent to/from the bridge). In the implementation of the built-in bridge, we've generally avoided logging in too much detail since that can pollute the mapper logs which contain a lot of other detail. I initially developed the bridge with concerns around debugging thin-edge.io specifically, but the bridge should also enable us to debug communication problems arising from the cloud too.

Describe the solution you'd like
I think the built-in bridge could perform detailed logging in a separate file. It would make sense to give the user some control over this (/the ability to disable it entirely since it could occupy rather a lot of disk space). There should probably be some basic logs in the main mapper logs, like what we have now which gives a broad indication of bridge health/backoffs in reconnecting, but doesn't give packet-by-packet descriptions of what's going on unless debug level logging is enabled.

Describe alternatives you've considered

Additional context