chore: fix logic for single line values and add test

Author: IvanJosipovic

src/KubernetesClient/KubernetesYaml.cs

@@ -92,11 +92,16 @@ public object ReadYaml(IParser parser, Type type, ObjectDeserializer rootDeseria
             public void WriteYaml(IEmitter emitter, object value, Type type, ObjectSerializer serializer)
             {
                 var obj = (byte[])value;
+                var strValue = Encoding.UTF8.GetString(obj);
+
+                // Check if the string is multi-line by looking for a newline character.
+                var scalarStyle = strValue.Contains('\n') ? ScalarStyle.Literal : ScalarStyle.Any;
+
                 emitter.Emit(new Scalar(
                     AnchorName.Empty,
                     TagName.Empty,
-                    Encoding.UTF8.GetString(obj),
-                    ScalarStyle.Literal,  // renders as |
+                    strValue,
+                    scalarStyle,
                     true,
                     true));
             }

tests/KubernetesClient.Tests/KubernetesYamlTests.cs

@@ -817,6 +817,30 @@ public void LoadSecret()
             Assert.Equal("Mzk1MjgkdmRnN0pi", Encoding.UTF8.GetString(result.Data["password"]));
         }
 
+        [Fact]
+        public void WriteSecret()
+        {
+            var kManifest = """
+apiVersion: v1
+data:
+  username: bXktYXBw
+  tls2.crt: |
+    -----BEGIN CERTIFICATE-----
+    FAKE CERT
+    FAKE CERT
+    FAKE CERT
+    -----END CERTIFICATE-----
+kind: Secret
+metadata:
+  name: test-secret
+""";
+
+            var result = KubernetesYaml.Deserialize<V1Secret>(kManifest, true);
+            var yaml = KubernetesYaml.Serialize(result);
+
+            Assert.Equal(kManifest, yaml);
+        }
+
         [Fact]
         public void DeserializeWithJsonPropertyName()
         {