Using a label to filter feature flags on Azure App Configuration

Program.cs

namespace MusicStore.Web
{
    public class Program
    {
       ...

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder => {
                    webBuilder.UseStartup<Startup>();
                })
                .ConfigureAppConfiguration((context, config) => {
                    var settings = config.Build();
                    var appConfigConnection = settings["ConnectionStrings:AppConfiguration"];

                    if (!string.IsNullOrEmpty(appConfigConnection))
                    {
                        config.AddAzureAppConfiguration(options =>
                        {
                            options
                                .Connect(settings["ConnectionStrings:AppConfiguration"])
                                .UseFeatureFlags(opt => {
                                    // Use the environment variable set on Azure App Service as the label.
                                    opt.Label = Environment.GetEnvironmentVariable("REGION_NAME")?.ToLowerInvariant().Trim().Replace(' ', '_');
                                });
                        });
                    }
                });
    }
}