Listener: Register callback API stub

This commit implements a stub API in Listener class to register callback
for all interfaces in correlated_properties.json. This commit also
implements a stub callback API which will be triggered whenever a
property change signal is detected.

Change-Id: Ifdaa2310b397ae9616d921ba2ee657f61dce753e
Signed-off-by: Souvik Roy <souvikroyofficial10@gmail.com>
diff --git a/vpd-manager/include/constants.hpp b/vpd-manager/include/constants.hpp
index f88944c..a41192e 100644
--- a/vpd-manager/include/constants.hpp
+++ b/vpd-manager/include/constants.hpp
@@ -236,5 +236,7 @@
     "/usr/share/vpd/50003_power_vs.json";
 static constexpr auto power_vs_50001_json =
     "/usr/share/vpd/50001_power_vs.json";
+static constexpr auto correlatedPropJsonFile =
+    "/usr/share/vpd/correlated_properties.json";
 } // namespace constants
 } // namespace vpd