chore: add BuildJsonConfig JSON roundtrip test

Author: filzrev

src/Docfx.Common/Json/JsonUtility.cs

@@ -90,6 +90,7 @@ private static bool IsSupported()
             switch (fullName)
             {
                 // TODO: Return `true` for types that support serialize/deserializenon with System.Text.Json.
+                case "Docfx.BuildJsonConfig":
                 case "Docfx.MergeJsonConfig":
 
                 case "Docfx.Build.Engine.XRefMap":

test/docfx.Tests/SerializationTests/JsonSerializationTest.BuildJsonConfig.cs

@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Docfx;
+using Docfx.Common;
+using FluentAssertions;
+
+namespace docfx.Tests;
+
+public partial class JsonSerializationTest
+{
+    [Theory]
+    [TestData<BuildJsonConfig>]
+    public void JsonSerializationTest_BuildJsonConfig(string path)
+    {
+        // Arrange
+        var model = TestData.Load<BuildJsonConfig>(path);
+
+        // Act/Assert
+        ValidateJsonRoundTrip(model);
+    }
+}

test/docfx.Tests/SerializationTests/TestData/BuildJsonConfig/buildJsonConfig_01.json

@@ -0,0 +1,41 @@
+{
+  "content": [
+    {
+      "files": [ "**/*.{md,yml}" ],
+      "exclude": [ "_site/**", "obj/**" ]
+    }
+  ],
+  "resource": [
+    {
+      "files": [ "**/images/**", "**/media/**", "codesnippet/**" ],
+      "exclude": [ "_site/**", "obj/**" ]
+    }
+  ],
+  "postProcessors": [ "ExtractSearchIndex" ],
+  "globalMetadata": {
+    "_appTitle": "docfx",
+    "_appName": "docfx",
+    "_appFooter": "<span>Supported by the <a href=\"https://dotnetfoundation.org\">.NET Foundation</a>. Made with <a href=\"https://dotnet.github.io/docfx\">docfx</a></span>",
+    "_googleAnalyticsTagId": "G-Q5N6XJHEX5",
+    "pdf": true
+  },
+  "markdownEngineProperties": {
+    "alerts": {
+      "TODO": "alert alert-secondary"
+    }
+  },
+  "sitemap": {
+    "baseUrl": "https://dotnet.github.io/docfx",
+    "priority": 0.5,
+    "changefreq": "daily"
+  },
+  "xref": [
+    "../.xrefmap.json"
+  ],
+  "output": "_site",
+  "template": [
+    "default",
+    "modern",
+    "template"
+  ]
+}