[idea] register callbacks with Config

[neurite]

Config changed -> Notify interested parties -> For example, reload the client with new configuration.

Interface:

refresh()
autoRefresh(interval)
registerCallback(key, callbackWithNewValue)

Note PropertiesConfig and JsonConfig do not know the sources of the configs. So a good place for these methods may be on DefaultConfig:

DefaultConfig.create()
        .autoRefresh(1000)
        .registerCallback("key", newVal -> {});

Or registering the callback is better close to where the key is used?

A custom class wrapping the DefaultConfig instance for managing refresh and callbacks?