Add SNMP event callback for error notification

Added callback support for SNMP events.

Parse the callback message and raise SNMP trap

Clients specify the object paths to watch and callbacks
to invoke in the config yaml.

Change-Id: I105652f65e4e1c5354c934c88e4d59866540f71c
Signed-off-by: Marri Devender Rao <devenrao@in.ibm.com>
diff --git a/src/data_types.hpp b/src/data_types.hpp
index 6be6431..cf0d69e 100644
--- a/src/data_types.hpp
+++ b/src/data_types.hpp
@@ -61,6 +61,14 @@
 using InterfacesAdded =
     std::map<std::string,
              std::map<std::string, sdbusplus::message::variant<T>>>;
+using Value =
+    sdbusplus::message::variant<bool, uint8_t, int16_t, uint16_t, int32_t,
+                                uint32_t, int64_t, uint64_t, std::string>;
+
+/** @brief ObjectManager.InterfacesAdded signal signature alias. */
+using Interface = std::string;
+using Property = std::string;
+using PathInterfacesAdded = std::map<Interface, std::map<Property, Value>>;
 
 /** @brief ObjectMapper.GetObject response signature alias. */
 using GetObject = std::map<MapperPath, std::vector<std::string>>;