Httpcontext.signIn() 执行了什么？

public static Task SignInAsync(this HttpContext context, string? scheme, ClaimsPrincipal principal, AuthenticationProperties? properties) =>context.RequestServices.GetService<IAuthenticationService>.SignInAsync(context, scheme, principal, properties);

public static IServiceCollection AddAuthenticationCore(this IServiceCollection services)
    {
        services.TryAddScoped<IAuthenticationService, AuthenticationService>();
        services.TryAddSingleton<IClaimsTransformation, NoopClaimsTransformation>(); // Can be replaced with scoped ones that use DbContext
        services.TryAddScoped<IAuthenticationHandlerProvider, AuthenticationHandlerProvider>();
        services.TryAddSingleton<IAuthenticationSchemeProvider, AuthenticationSchemeProvider>();
        return services;
    }

public async Task<IAuthenticationHandler?> GetHandlerAsync(HttpContext context, string authenticationScheme)
    {var scheme = await Schemes.GetSchemeAsync(authenticationScheme);var handler = (context.RequestServices.GetService(scheme.HandlerType) ??
            ActivatorUtilities.CreateInstance(context.RequestServices, scheme.HandlerType))
            as IAuthenticationHandler;
        if (handler != null)
        {
            await handler.InitializeAsync(scheme, context);
            _handlerMap[authenticationScheme] = handler;
        }
        return handler;
    }

    public static AuthenticationBuilder AddCookie(this AuthenticationBuilder builder, string authenticationScheme, string? displayName, Action<CookieAuthenticationOptions> configureOptions)
    {
        builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<IPostConfigureOptions<CookieAuthenticationOptions>, PostConfigureCookieAuthenticationOptions>());
        builder.Services.AddOptions<CookieAuthenticationOptions>(authenticationScheme).Validate(o => o.Cookie.Expiration == null, "Cookie.Expiration is ignored, use ExpireTimeSpan instead.");
        return builder.AddScheme<CookieAuthenticationOptions, CookieAuthenticationHandler>(authenticationScheme, displayName, configureOptions);
    }