ASP.NET核心2.1中缺少AddSignIn方法

public void ConfigureServices(IServiceCollection services)
{
    // 添加身份验证服务
    services.AddAuthentication(options =>
    {
        options.DefaultAuthenticateScheme = "Cookies";
        options.DefaultSignInScheme = "Cookies";
        options.DefaultChallengeScheme = "OpenIdConnect";
    })
    .AddCookie("Cookies") // 添加Cookie身份验证中间件
    .AddOpenIdConnect("OpenIdConnect", options =>
    {
        // 配置OpenID Connect身份验证选项
        options.Authority = "https://example.com";
        options.ClientId = "your-client-id";
        options.ClientSecret = "your-client-secret";
        options.ResponseType = "code";
        options.Scope.Add("openid");
        options.Scope.Add("profile");
        options.SaveTokens = true;
    });

    // 其他服务配置...
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    // 其他中间件配置...

    // 启用身份验证中间件
    app.UseAuthentication();

    // 其他配置...
}