Access token management for HttpClient

Startup.cs

// add IdentityModel.AspNetCore package
using Microsoft.Extensions.DependencyInjection;
using IdentityModel.Client;

public class Startup
{
    /* removed all other code for brevity */

    public void ConfigureServices(IServiceCollection services)
    {
        string tokenClientName = "DemoClient";

        services.AddAccessTokenManagement(options =>
        {
            options.Client.Clients.Add(tokenClientName, new ClientCredentialsTokenRequest
            {
                Address = "https://[authority]/connect/token",
                ClientId = "clientId",
                ClientSecret = "Client Secret",
                Scope = "Scope"
            });
        });

        services.AddHttpClient<MyDemoHttpClient>().AddClientAccessTokenHandler(tokenClientName);
    }
}