Added KubernetesYaml.SerializeAll method (#947)

tests/KubernetesClient.Tests/KubernetesYamlTests.cs

@@ -325,6 +325,27 @@ metadata:
             Assert.Equal(content, serialized);
         }
 
+        [Fact]
+        public void SerializeAll()
+        {
+            var pods = new List<object>
+            {
+                new V1Pod() { ApiVersion = "v1", Kind = "Pod", Metadata = new V1ObjectMeta() { Name = "foo" } },
+                new V1Pod() { ApiVersion = "v1", Kind = "Pod", Metadata = new V1ObjectMeta() { Name = "bar" } },
+            };
+            var yaml = KubernetesYaml.SerializeAll(pods);
+            Assert.Equal(
+                ToLines(@"apiVersion: v1
+kind: Pod
+metadata:
+  name: foo
+---
+apiVersion: v1
+kind: Pod
+metadata:
+  name: bar"), ToLines(yaml));
+        }
+
         [Fact]
         public void WriteToString()
         {