Add Fan item interface

This interface identifies an associated inventory item
as a Fan.

Signed-off-by: Anthony Wilson <wilsonan@us.ibm.com>
Change-Id: I2edeaad42df44c19872fb0489ac74d940f289cc3
diff --git a/presence/fan.cpp b/presence/fan.cpp
index 71f17c7..823de29 100644
--- a/presence/fan.cpp
+++ b/presence/fan.cpp
@@ -31,6 +31,7 @@
 static const auto invNamespace = "/xyz/openbmc_project/inventory"s;
 static const auto itemIface = "xyz.openbmc_project.Inventory.Item"s;
 static const auto invMgrIface = "xyz.openbmc_project.Inventory.Manager"s;
+static const auto fanIface = "xyz.openbmc_project.Inventory.Item.Fan"s;
 
 void setPresence(const Fan& fan, bool newState)
 {
@@ -48,7 +49,10 @@
                 {"Present"s, newState},
                 {"PrettyName"s, std::get<0>(fan)},
             }
-        }}
+        },
+        {
+            fanIface, {}
+        }},
     }};
 
     util::SDBusPlus::lookupAndCallMethod(