ConfigServer+LibConfig: Add way for clients to listen for config changes

This patch adds a Config::Listener abstract class that anyone can
inherit from and receive notifications when configuration values change.

We don't yet monitor file system changes, so these only work for changes
made by ConfigServer itself.

In order to receive these notifications, clients must monitor the domain
by calling monitor_domain(). Only pledged domains can be monitored.

Note that the client initiating the change does not get notified.

0 files changed, 0 insertions, 0 deletions