add name assignment config

Change-Id: I7a67759c50ed9986a8bcf6db814c372a0ee418d5
diff --git a/src/ndncert-common.hpp b/src/ndncert-common.hpp
index 4da43c9..b14cd12 100644
--- a/src/ndncert-common.hpp
+++ b/src/ndncert-common.hpp
@@ -123,6 +123,7 @@
 const std::string CONFIG_CHALLENGE = "challenge";
 const std::string CONFIG_CERTIFICATE = "certificate";
 const std::string CONFIG_REDIRECTION = "redirect-to";
+const std::string CONFIG_NAME_ASSIGNMENT = "name-assignment";
 
 
 // NDNCERT Status Enum