Built-in configuration binder.
Object ConfigBinder
This binder is used to bind service configuration values to Nest variables.
The reason to do this convolute thing is that listeners can set themselves into ServiceVar instances, and in this way they can be notified of even configuration variables set in the service.
Of course, a service is not REQUIRED to offer all its configuration variables publically in this way. It can just receive the configuration data and use it turing the startup or run phase.
However, if some relevant automated variable has any utility in being published and universally know, this is a useful way to automatically store its value from the configuration of the service into it, and eventually notify listeners.