Kubernetes.Classic: add support for netstandard2.0 and net48 (#808)

* support gh nuget (#11)

* trim to fit net48

* add net48 support

* add very test framework

* add test body

* Revert "support gh nuget (#11)"

This reverts commit 5cdaf59690170be44e4554485fb2e89785a6a1cf.

tests/KubernetesClient.Classic.Tests/SimpleTests.cs

@@ -0,0 +1,81 @@
+using System.IO;
+using System.Net;
+using System.Net.Sockets;
+using System.Threading.Tasks;
+using Xunit;
+using k8s.Models;
+
+namespace k8s.tests;
+
+public class BasicTests
+{
+    // TODO: fail to setup asp.net core 6 on net48
+    private class DummyHttpServer : System.IDisposable
+    {
+        private TcpListener server;
+        private readonly Task loop;
+        private volatile bool running = false;
+
+        public string Addr => $"http://{server.LocalEndpoint}";
+
+        public DummyHttpServer(object obj)
+        {
+            server = new TcpListener(IPAddress.Parse("127.0.0.1"), 0);
+            server.Start();
+            running = true;
+            loop = Task.Run(async () =>
+            {
+                while (running)
+                {
+                    var result = KubernetesJson.Serialize(obj);
+
+                    var client = await server.AcceptTcpClientAsync().ConfigureAwait(false);
+                    var stream = client.GetStream();
+                    stream.Read(new byte[1024], 0, 1024); // TODO ensure full header
+
+                    var writer = new StreamWriter(stream);
+                    await writer.WriteLineAsync("HTTP/1.0 200 OK").ConfigureAwait(false);
+                    await writer.WriteLineAsync("Content-Length: " + result.Length).ConfigureAwait(false);
+                    await writer.WriteLineAsync("Content-Type: application/json").ConfigureAwait(false);
+                    await writer.WriteLineAsync().ConfigureAwait(false);
+                    await writer.WriteLineAsync(result).ConfigureAwait(false);
+
+                    await writer.FlushAsync().ConfigureAwait(false);
+                    client.Close();
+                }
+            });
+        }
+
+        public void Dispose()
+        {
+            try
+            {
+                running = false;
+                server.Stop();
+                loop.Wait();
+                loop.Dispose();
+            }
+            catch
+            {
+                // ignore
+            }
+        }
+    }
+
+    [Fact]
+    public async Task QueryPods()
+    {
+        using var server = new DummyHttpServer(new V1Pod()
+        {
+            Metadata = new V1ObjectMeta()
+            {
+                Name = "pod0",
+            },
+        });
+        var client = new Kubernetes(new KubernetesClientConfiguration { Host = server.Addr });
+
+        var pod = await client.ReadNamespacedPodAsync("pod", "default").ConfigureAwait(false);
+
+        Assert.Equal("pod0", pod.Metadata.Name);
+    }
+}