.NET 9 OpenApi using with FastEndpoints and Scalar

Program.cs

using FastEndpoints;
using Scalar.AspNetCore;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddOpenApi();
builder.Services.AddFastEndpoints()
    .AddOpenApiDocument();

var app = builder.Build();

app.UseFastEndpoints()
    .UseOpenApi();

if (app.Environment.IsDevelopment())
{
    app.MapOpenApi();
    app.MapScalarApiReference();
}

app.UseHttpsRedirection();

app.Run();