mountRouter(path, router) {
        if (arguments.length === 1) {
            router = path;
            debug(this.name + ': mountRouter: ' + router.name);
            this._router.use(router);
        } else {
            registry.setRoute(this.name, path);
            debug(this.name + ': mountRouter: ' + router.name + ' at ' + path);
            this._router.use(path, router);
        }
    }
@description Mount a router on a router (sub-routing)
@param {String | import('express').Router} path
@param {import('express').Router} [router]