EventService: Add ResourceEvent registries

This commit adds new files for DMTF resource registry
and corresponding json message definitions.

Tested by:
  1. GET https://${bmc}/redfish/v1/Registries
  2. GET https://${bmc}/redfish/v1/Registries/ResourceEvent
  3. GET https://${bmc}/redfish/v1/Registries/ResourceEvent/ResourceEvent
  4. Redfish Validator passed ( giving out messages as == Severity:
       The given property is deprecated by revision: This property has been deprecated
       in favor of MessageSeverity, which ties the values to the enumerations defined
       for the Health property within Status.)

Signed-off-by: Sunitha Harish <sunithaharish04@gmail.com>
Change-Id: Iacbedaeca85c0dcfc955bcf9b10973c0d47c98e0
diff --git a/redfish-core/include/resource_messages.hpp b/redfish-core/include/resource_messages.hpp
new file mode 100644
index 0000000..4ff1c86
--- /dev/null
+++ b/redfish-core/include/resource_messages.hpp
@@ -0,0 +1,42 @@
+#pragma once
+
+namespace redfish
+{
+namespace messages
+{
+
+nlohmann::json ResourceChanged(void)
+{
+    return nlohmann::json{
+        {"EventType", "ResourceChanged"},
+        {"MessageId", "ResourceEvent.1.0.3.ResourceChanged"},
+        {"Message", "One or more resource properties have changed."},
+        {"MessageArgs", {}},
+        {"Severity", "OK"},
+        {"MessageSeverity", "OK"}};
+}
+
+nlohmann::json ResourceCreated(void)
+{
+    return nlohmann::json{
+        {"EventType", "ResourceAdded"},
+        {"MessageId", "ResourceEvent.1.0.3.ResourceCreated"},
+        {"Message", "The resource has been created successfully."},
+        {"MessageArgs", {}},
+        {"Severity", "OK"},
+        {"MessageSeverity", "OK"}};
+}
+
+nlohmann::json ResourceRemoved(void)
+{
+    return nlohmann::json{
+        {"EventType", "ResourceRemoved"},
+        {"MessageId", "ResourceEvent.1.0.3.ResourceRemoved"},
+        {"Message", "The resource has been removed successfully."},
+        {"MessageArgs", {}},
+        {"Severity", "OK"},
+        {"MessageSeverity", "OK"}};
+}
+
+} // namespace messages
+} // namespace redfish