kubernetes provider (#772)

* feat: Kubernetes ServiceDiscoveryProvider

* 编写k8s测试例子

* feat：fix kube config

* feat： remove port

* feat ： complete the k8s test

* feat :  add kubeserviceDiscovery test

* feat : add kube provider unittest

* feat :add kubetnetes docs

how to use ocelot with kubetnetes docs

* keep the configuration as simple as possible, no qos, no cache

* fix: use http

* add PollingKubeServiceDiscovery

* feat : refactor logger

* feat : add  pollkube docs

* feat：Remove unnecessary code

* feat ： code-block json

test/Ocelot.UnitTests/Kubernetes/PollingKubeServiceDiscoveryProviderTests.cs

@@ -0,0 +1,82 @@
+using Moq;
+using Ocelot.Infrastructure;
+using Ocelot.Logging;
+using Ocelot.Provider.Kubernetes;
+using Ocelot.ServiceDiscovery.Providers;
+using Ocelot.Values;
+using Shouldly;
+using System;
+using System.Collections.Generic;
+using System.Text;
+using TestStack.BDDfy;
+using Xunit;
+
+namespace Ocelot.UnitTests.Kubernetes
+{
+    public class PollingKubeServiceDiscoveryProviderTests
+    {
+        private readonly int _delay;
+        private PollKube _provider;
+        private readonly List<Service> _services;
+        private readonly Mock<IOcelotLoggerFactory> _factory;
+        private readonly Mock<IOcelotLogger> _logger;
+        private readonly Mock<IServiceDiscoveryProvider> _kubeServiceDiscoveryProvider;
+        private List<Service> _result;
+
+        public PollingKubeServiceDiscoveryProviderTests()
+        {
+            _services = new List<Service>();
+            _delay = 1;
+            _factory = new Mock<IOcelotLoggerFactory>();
+            _logger = new Mock<IOcelotLogger>();
+            _factory.Setup(x => x.CreateLogger<PollKube>()).Returns(_logger.Object);
+            _kubeServiceDiscoveryProvider = new Mock<IServiceDiscoveryProvider>();
+        }
+
+        [Fact]
+        public void should_return_service_from_kube()
+        {
+            var service = new Service("", new ServiceHostAndPort("", 0), "", "", new List<string>());
+
+            this.Given(x => GivenKubeReturns(service))
+                .When(x => WhenIGetTheServices(1))
+                .Then(x => ThenTheCountIs(1))
+                .BDDfy();
+        }
+
+        private void GivenKubeReturns(Service service)
+        {
+            _services.Add(service);
+            _kubeServiceDiscoveryProvider.Setup(x => x.Get()).ReturnsAsync(_services);
+        }
+
+        private void ThenTheCountIs(int count)
+        {
+            _result.Count.ShouldBe(count);
+        }
+
+        private void WhenIGetTheServices(int expected)
+        {
+            _provider = new PollKube(_delay, _factory.Object, _kubeServiceDiscoveryProvider.Object);
+
+            var result = Wait.WaitFor(3000).Until(() => {
+                try
+                {
+                    _result = _provider.Get().GetAwaiter().GetResult();
+                    if (_result.Count == expected)
+                    {
+                        return true;
+                    }
+
+                    return false;
+                }
+                catch (Exception)
+                {
+                    return false;
+                }
+            });
+
+            result.ShouldBeTrue();
+        }
+    }
+}