Fix kubeconfig extension handling (#556)

Extensions on kubeconfig files are stored as a list of NamedExtension objects, not a dictionary.

tests/KubernetesClient.Tests/KubernetesClientConfigurationTests.cs

@@ -1,10 +1,11 @@
+using k8s.Exceptions;
+using k8s.KubeConfigModels;
 using System;
 using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
 using System.Threading;
-using k8s.Exceptions;
-using k8s.KubeConfigModels;
+using System.Threading.Tasks;
 using Xunit;
 
 namespace k8s.Tests
@@ -372,6 +373,14 @@ namespace k8s.Tests
             Assert.NotNull(cfg.Host);
         }
 
+        [Fact]
+        public async Task ContextWithClusterExtensions()
+        {
+            var path = Path.GetFullPath("assets/kubeconfig.cluster-extensions.yml");
+
+            var cfg = await KubernetesClientConfiguration.BuildConfigFromConfigFileAsync(new FileInfo(path)).ConfigureAwait(false);
+        }
+
         /// <summary>
         ///     Ensures Kube config file is loaded from explicit file
         /// </summary>
@@ -525,8 +534,8 @@ namespace k8s.Tests
                 new FileInfo(path), new FileInfo(path),
             });
 
-            Assert.Equal(1, cfg.Extensions.Count);
-            Assert.Equal(1, cfg.Preferences.Count);
+            Assert.Single(cfg.Extensions);
+            Assert.Single(cfg.Preferences);
         }
 
         /// <summary>

tests/KubernetesClient.Tests/assets/kubeconfig.cluster-extensions.yml

@@ -0,0 +1,31 @@
+apiVersion: v1
+clusters:
+- cluster:
+    extensions:
+    - extension:
+        last-update: Wed, 27 Jan 2021 11:44:41 UTC
+        provider: minikube.sigs.k8s.io
+        version: v1.17.0
+      name: cluster_info
+    server: https://192.168.49.2:8443
+  name: minikube
+contexts:
+- context:
+    cluster: minikube
+    extensions:
+    - extension:
+        last-update: Wed, 27 Jan 2021 11:44:41 UTC
+        provider: minikube.sigs.k8s.io
+        version: v1.17.0
+      name: context_info
+    namespace: default
+    user: minikube
+  name: minikube
+current-context: minikube
+kind: Config
+preferences: {}
+users:
+- name: minikube
+  user:
+    password: secret
+    username: admin

tests/KubernetesClient.Tests/assets/kubeconfig.preferences-extensions.yml

@@ -3,4 +3,6 @@ kind: Config
 preferences:
   colors: true
 extensions:
-  foo: bar
+  - name: foo
+    extension:
+      foo: bar