Add another couple of constructors to Fix #279 (#302)

* Add support for HttpClientFactory with KubernetesClientConfiguration

* Add an example with http client factory

* ensure sample uses the latest version of C#

examples/httpClientFactory/Program.cs

@@ -0,0 +1,46 @@
+using k8s;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.DependencyInjection;
+using System.Threading.Tasks;
+
+namespace httpClientFactory
+{
+    internal class Program
+    {
+        public static async Task Main(string[] args)
+        {
+            // Learn more about generic hosts at https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/generic-host
+            using (var host = new HostBuilder()
+                .ConfigureLogging((logging) =>
+                {
+                    logging.AddConsole();
+                })
+                .ConfigureServices((hostBuilderContext, services) =>
+                {
+                    // Ideally this config would be read from the .net core config constructs,
+                    // but that has not been implemented in the KubernetesClient library at
+                    // the time this sample was created.
+                    var config = KubernetesClientConfiguration.BuildDefaultConfig();
+                    services.AddSingleton(config);
+
+                    // Setup the http client
+                    services.AddHttpClient("K8s")
+                        .AddTypedClient<IKubernetes>((httpClient, serviceProvider) =>
+                        {
+                            return new Kubernetes(
+                                serviceProvider.GetRequiredService<KubernetesClientConfiguration>(),
+                                httpClient);
+                        });
+
+                    // Add the class that uses the client
+                    services.AddHostedService<PodListHostedService>();
+                })
+                .Build())
+            {
+                await host.StartAsync().ConfigureAwait(false);
+                await host.StopAsync().ConfigureAwait(false);
+            }
+        }
+    }
+}