async capabilities() {
    const config = JSON.parse(JSON.stringify(global.kuzzle.config));
    const publicApi = await this.publicApi();
    const services = {};
    const plugins = {};

    for (const plugin of config.plugins.common.include) {
      plugins[plugin] = {
        version: packagejson.dependencies[plugin],
      };
    }

    for (const [name, info] of Object.entries(config.services)) {
      if (info.backend !== undefined) {
        services[name] = {
          backend: info.backend,
          version: this._info[info.backend].version,
        };
      }
    }

    return {
      limits: config.limits,
      plugins: plugins,
      routes: publicApi,
      services: services,
      version: config.version,
    };
  }
Returns the Kuzzle capabilities
@returns {Promise<Object>}