public static AuditActor system(@Nonnull NodeId nodeId) {
        return new AutoValue_AuditActor(URN_GRAYLOG_NODE + requireNonNull(nodeId, "nodeId must not be null").getNodeId());
    }
@Test
    public void testSystem() {
        final NodeId nodeId = new SimpleNodeId("28164cbe-4ad9-4c9c-a76e-088655aa78892");
        final AuditActor actor = AuditActor.system(nodeId);

        assertThat(actor.urn()).isEqualTo("urn:graylog:node:28164cbe-4ad9-4c9c-a76e-088655aa78892");
    }