NPA-4670: Add App Header to Auth Header Policy

Author: LeoKHoward

proxies/live/apiproxy/policies/AssignMessage.AddAuthHeaders.xml

@@ -6,6 +6,7 @@
             <Header name="accesstoken.auth_level">{toUpperCase(accesstoken.auth_level)}</Header>
             <Header name="accesstoken.auth_user_id">{accesstoken.auth_user_id}</Header>
             <Header name="accesstoken.auth_vot">{jwt.DecodeAccessTokenJWT.claim.vot}</Header>
+            <Header name="app">{app}</Header>
         </Headers>
     </Add>
     <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>