Make JsonSerializer content type static (#118)

Author: Sakeeb91

src/FlowCtl.Infrastructure/Serialization/JsonSerializer.cs

@@ -7,7 +7,10 @@ namespace FlowCtl.Infrastructure.Serialization;
 
 public class JsonSerializer : IJsonSerializer
 {
-    public string ContentMineType => "application/json";
+    /// <summary>
+    /// Static JSON content type reference that callers can reuse without instantiating the serializer.
+    /// </summary>
+    public static string ContentMineType => "application/json";
 
     public string Serialize(object? input)
     {

tests/FlowCtl.Infrastructure.UnitTests/Serialization/JsonSerializerTests.cs

@@ -6,6 +6,16 @@ namespace FlowCtl.Infrastructure.UnitTests.Serialization;
 
 public class JsonSerializerTests
 {
+    [Fact]
+    public void ContentMineType_ShouldExposeJsonMimeTypeWithoutInstance()
+    {
+        // Act
+        var mimeType = JsonSerializer.ContentMineType;
+
+        // Assert
+        Assert.Equal("application/json", mimeType);
+    }
+
     [Fact]
     public void Serialize_ShouldThrowFlowSynxException_WhenInputIsNull()
     {