Add associations::Manager class

This class will handle creating the org.openbmc.Associations
D-Bus interfaces on inventory paths if it has been told to
by a JSON configuration file.

Every time PIM creates a new inventory path, this class will
check to see if any associations need to be created.

This functionality is optional, and is off by default.  To
enable it, the --enable-associations configure option needs to
be used.

This commit just introduces the class.

Change-Id: I70045b768f3db683bcfac0c7d4bc9798eb10a5c5
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/manager.hpp b/manager.hpp
index cabbac9..5ad4f44 100644
--- a/manager.hpp
+++ b/manager.hpp
@@ -5,6 +5,9 @@
 #include "interface_ops.hpp"
 #include "serialize.hpp"
 #include "types.hpp"
+#ifdef CREATE_ASSOCIATIONS
+#include "association_manager.hpp"
+#endif
 
 #include <any>
 #include <map>
@@ -205,6 +208,11 @@
 
     /** @brief A container of pimgen generated factory methods.  */
     static const Makers _makers;
+
+    /** @brief Handles creating mapper associations for inventory objects */
+#ifdef CREATE_ASSOCIATIONS
+    associations::Manager _associations;
+#endif
 };
 
 } // namespace manager