Use case for C# 9's attributes on local functions

Program.cs

using System.Security.Claims;
using System.Text.Encodings.Web;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

Host.CreateDefaultBuilder(args)
    .ConfigureWebHostDefaults(webBuilder =>
    {
        webBuilder.ConfigureServices(services =>
        {
            services
              .AddAuthentication("MyScheme")
              .AddScheme<DummyAuthenticationOptions, DummyAuthenticationHandler>("MyScheme", options => { });
            services.AddAuthorization();
        })
        .Configure(app =>
        {
            app.UseRouting();
            app.UseAuthentication();
            app.UseAuthorization();
            app.UseEndpoints(endpoints =>
            {
                static async Task SayHello(HttpContext context) => await context.Response.WriteAsync("Public view");
                endpoints.MapGet("/", SayHello);

                [Authorize(AuthenticationSchemes = "MyScheme", Roles = "Admin")]
                static async Task AdminsOnly(HttpContext context) => await context.Response.WriteAsync("Admin view");
                endpoints.MapGet("/secret", AdminsOnly);
            });
        });
    })
    .Build().Run();

public class DummyAuthenticationOptions : AuthenticationSchemeOptions { }

internal class DummyAuthenticationHandler : AuthenticationHandler<DummyAuthenticationOptions>
{
    public DummyAuthenticationHandler(IOptionsMonitor<DummyAuthenticationOptions> options,
        ILoggerFactory logger, UrlEncoder encoder, ISystemClock clock)
        : base(options, logger, encoder, clock) { }

    protected override Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        var claims = new[]
        {
        new Claim(ClaimTypes.NameIdentifier, "Rainer"),
        new Claim(ClaimTypes.Role, "Admin")
      };

        var claimsPrincipal = new ClaimsPrincipal(new ClaimsIdentity(claims, Scheme.Name));
        var ticket = new AuthenticationTicket(claimsPrincipal,
            new AuthenticationProperties { IsPersistent = false }, Scheme.Name);
        return Task.FromResult(AuthenticateResult.Success(ticket));
    }
}