async createSSRServerConfig() {
        return await this.webpackConfig.server({
            extendWithWebpackChain: async (serverConfig, {type}) => {
                if (type === 'server') {
                    serverConfig.name = 'ssrserver';
                    serverConfig
                        .context(this.config.globals.rootDir)
                        .entry(DEFAULT_ENTRY_NAME).add('./core/entry-server.js');
                }
            }
        });
    }
create a webpack config which will be compiled later

@return {Object} SSRServerConfig webpack config for SSRServer