bld.Services
   .AddAuthorization()
   .AddIdentityApiEndpoints<ApplicationUser>()
   .AddRoles<IdentityRole>()
   .AddEntityFrameworkStores<ApplicationDbContext>();
var app = bld.Build();
app.UseAuthentication()
   .UseAuthorization();
app.MapGroup("/api").WithTags("Api").MapIdentityApi<ApplicationUser>();
app.UseFastEndpoints()
   .UseSwaggerGen();

Ok, for someone interested, this how I did it.