Is your feature improvement request related to a problem? Please describe.
Working with a customer that is utilizing cellular devices. They have strict bandwidth requirements where even the frequency of keep-alive messages can impact the negotiated contract with their cellular provider. The proposed option would allow them to limit the number of MQTT keep alive messages being sent by their device and ultimately the amount of bandwidth that passes through the cellular connection. This could impact any device that is utilizing a cellular connection.

Describe the solution you'd like
Would like the option to either be set through the tedge cli and saved as a tedge configuration option. Could also be a persistent entry in the c8y_bridge.conf file. I have found that when I manually add it to the configuration file and restart Mosquitto service through sysctl, I can see the behavior I want. The problem with this is that the configuration file gets recreated when a tedge reconnect c8y command is run and the change needs to be reapplied.

Describe alternatives you've considered
The workaround that we are investigating in the short term is scripting the modification of the bridge configuration file and then restarting the Mosquitto service. This is a bit cumbersome and technically may not be feasible given the additional start up latency that it will introduce. We have also considered creating a new configuration file and storing it in the /etc/mosquitto/conf.d directory (this is already referenced in the mosquitto.conf file, similar to /etc/tedge/mosquitto_conf) . I think this fails because the bridge seems to be created by some logic in thin-edge where it builds out the connection and the keepalive_interval needs to be in the context of that connection. Because it is outside of that in this config file we have created, it prevents Thin-Edge from starting.

Additional context
I don't think there are any screenshots that are needed. I'm happy to jump on a call and show any of things I mentioned above if that is helpful.