main UPDATE support multiple subscriptions to streams (#1808)

Currently, the NETCONF server makes an assumption that it will be the
only entity which manages this container. With our RESTCONF server, this
is no longer the case. Unless there's a systemwide "notification daemon"
which will be in charge of this, the only reasonable choice is, IMHO, to
rely on the usual rules of data merging as provided by sysrepo.

Author: jktjkt

src/main.c

@@ -1320,7 +1320,12 @@ server_data_subscribe(void)
     }
 
     /* operational data */
-    SR_OPER_SUBSCR(mod_name, "/ietf-subscribed-notifications:streams", srsn_oper_data_streams_cb);
+    rc = sr_oper_get_subscribe(np2srv.sr_sess, mod_name, "/ietf-subscribed-notifications:streams",
+            srsn_oper_data_streams_cb, NULL, SR_SUBSCR_OPER_MERGE, &np2srv.sr_data_sub);
+    if (rc != SR_ERR_OK) {
+        ERR("Subscribing for providing \"%s\" state data failed (%s).", mod_name, sr_strerror(rc));
+        goto error;
+    }
     rc = sr_oper_get_subscribe(np2srv.sr_sess, mod_name, "/ietf-subscribed-notifications:subscriptions",
             np2srv_oper_sub_ntf_subscriptions_cb, NULL, SR_SUBSCR_OPER_MERGE, &np2srv.sr_data_sub);
     if (rc != SR_ERR_OK) {