feat: support emqx_conf:update([license],Conf)

lib-ee/emqx_license/src/emqx_license.erl

@@ -122,9 +122,9 @@ do_update({key, Content}, Conf) when is_binary(Content); is_list(Content) ->
         {error, Reason} ->
             erlang:throw(Reason)
     end;
-%% We don't do extra action when update license's watermark.
-do_update(_Other, Conf) ->
-    Conf.
+do_update(NewConf, _PrevConf) ->
+    #{<<"key">> := NewKey} = NewConf,
+    do_update({key, NewKey}, NewConf).
 
 check_max_clients_exceeded(MaxClients) ->
     emqx_license_resources:connection_count() > MaxClients * 1.1.