Csharp 身份验证中间件如何处理多个方案

我们知道我们可以使用多种方案对用户进行身份验证，例如

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(JwtBearerDefaults.AuthenticationScheme,
        options => builder.Configuration.Bind("JwtSettings", options))
    .AddCookie(CookieAuthenticationDefaults.AuthenticationScheme,
        options => builder.Configuration.Bind("CookieSettings", options));

但根据AuthenticationMiddleware代码: https://source.dot.net/#Microsoft.AspNetCore.Authentication/AuthenticationMiddleware.cs,50个

public async Task Invoke(HttpContext context)
{
    // ...
    var handlers = context.RequestServices.GetRequiredService<IAuthenticationHandlerProvider>();
    foreach (var scheme in await Schemes.GetRequestHandlerSchemesAsync())
    {
        var handler = await handlers.GetHandlerAsync(context, scheme.Name) as IAuthenticationRequestHandler;
        if (handler != null && await handler.HandleRequestAsync())
        {
            return;
        }
    }

    var defaultAuthenticate = await Schemes.GetDefaultAuthenticateSchemeAsync();
    if (defaultAuthenticate != null)
    {
        var result = await context.AuthenticateAsync(defaultAuthenticate.Name);
        // ...
    }

    await _next(context);
}

foreach人似乎从一开始就采用了多种方案.然而，它使用的是IAuthenticationRequestHandler，而不是IAuthenticationHandler.

因此，当我们调用AddCookie扩展方法时，我们将处理程序类型的方案添加为CookieAuthenticationHandler(https://source.dot.net/#Microsoft.AspNetCore.Authentication.Cookies/CookieExtensions.cs,81) 接口实现链为:

public class CookieAuthenticationHandler : SignInAuthenticationHandler<CookieAuthenticationOptions>

public abstract class SignInAuthenticationHandler<TOptions> : SignOutAuthenticationHandler<TOptions>, IAuthenticationSignInHandler

// ...

如果我们一直向上跟踪，SignInAuthenticationHandler就不会实现IAuthenticationRequestHandler，那么AuthenticationMiddleware如何处理多个方案和调用多个处理程序呢？据我所知，只有默认方案才适用吗？