issue#32 Implement FEAT05 - Add priority in NSD IFA014

Signed-off-by: Preethika <preethika.p@tataelxsi.co.in>

src/yang/etsi-nfv-ns.yang

@@ -1694,6 +1694,22 @@ submodule etsi-nfv-ns {
         }
       }
 
+      leaf priority {
+        type uint32;
+        description
+          "Specifies the priority for the NS instance.
+
+           The allowed range will be reasonably high. The 'zero'
+           value will express the highest priority and the fact
+           that the NS instance based on this DF cannot be
+           pre-empted during resource allocation.
+
+           Examples for the usage of priority include conflict
+           resolution in case of resource shortage.";
+        reference
+          "GS NFV IFA014: Section 6.3.2.2 NsDf information element";
+      }
+
       leaf service-availability-level {
         type uint32;
         description