show response headers so sandbox users can see location of registered…

… pointers

proxies/sandbox/apiproxy/policies/AssignMessage.AddCors.xml

@@ -5,6 +5,7 @@
         <Headers>
             <Header name="Access-Control-Allow-Origin">{request.header.origin}</Header>
             <Header name="Access-Control-Allow-Headers">origin, x-requested-with, accept, content-type, nhsd-session-urid, x-correlation-id, x-request-id, nhsd-end-user-organisation-ods</Header>
+            <Header name="Access-Control-Expose-Headers">content-type,location,x-correlation-id,x-request-id</Header>
             <Header name="Access-Control-Max-Age">3628800</Header>
             <Header name="Access-Control-Allow-Methods">GET, PUT, POST, DELETE</Header>
         </Headers>