Make the API content response builder extendable

src/Umbraco.Cms.Api.Delivery/Json/DeliveryApiJsonTypeResolver.cs

@@ -12,23 +12,36 @@
     {
         JsonTypeInfo jsonTypeInfo = base.GetTypeInfo(type, options);
 
+        Type[] derivedTypes = GetDerivedTypes(jsonTypeInfo);
+        if (derivedTypes.Length > 0)
+        {
+            ConfigureJsonPolymorphismOptions(jsonTypeInfo, derivedTypes);
+        }
+
+        return jsonTypeInfo;
+    }
+
+    protected virtual Type[] GetDerivedTypes(JsonTypeInfo jsonTypeInfo)
+    {
         if (jsonTypeInfo.Type == typeof(IApiContent))
         {
-            ConfigureJsonPolymorphismOptions(jsonTypeInfo, typeof(ApiContent));
+            return new[] { typeof(ApiContent) };
         }
-        else if (jsonTypeInfo.Type == typeof(IApiContentResponse))
+
+        if (jsonTypeInfo.Type == typeof(IApiContentResponse))
         {
-            ConfigureJsonPolymorphismOptions(jsonTypeInfo, typeof(ApiContentResponse));
+            return new[] { typeof(ApiContentResponse) };
         }
-        else if (jsonTypeInfo.Type == typeof(IRichTextElement))
+
+        if (jsonTypeInfo.Type == typeof(IRichTextElement))
         {
-            ConfigureJsonPolymorphismOptions(jsonTypeInfo, typeof(RichTextRootElement), typeof(RichTextGenericElement), typeof(RichTextTextElement));
+            return new[] { typeof(RichTextRootElement), typeof(RichTextGenericElement), typeof(RichTextTextElement) };
         }
 
-        return jsonTypeInfo;
+        return Array.Empty<Type>();
     }
 
-    private void ConfigureJsonPolymorphismOptions(JsonTypeInfo jsonTypeInfo, params Type[] derivedTypes)
+    protected void ConfigureJsonPolymorphismOptions(JsonTypeInfo jsonTypeInfo, params Type[] derivedTypes)
     {
         jsonTypeInfo.PolymorphismOptions = new JsonPolymorphismOptions
         {

src/Umbraco.Core/DeliveryApi/ApiContentResponseBuilder.cs

@@ -1,11 +1,10 @@
 using Umbraco.Cms.Core.Models.DeliveryApi;
 using Umbraco.Cms.Core.Models.PublishedContent;
-using Umbraco.Cms.Core.Routing;
 using Umbraco.Extensions;
 
 namespace Umbraco.Cms.Core.DeliveryApi;
 
-public sealed class ApiContentResponseBuilder : ApiContentBuilderBase<IApiContentResponse>, IApiContentResponseBuilder
+public class ApiContentResponseBuilder : ApiContentBuilderBase<IApiContentResponse>, IApiContentResponseBuilder
 {
     private readonly IApiContentRouteBuilder _apiContentRouteBuilder;
 
@@ -14,6 +13,12 @@ public ApiContentResponseBuilder(IApiContentNameProvider apiContentNameProvider,
         => _apiContentRouteBuilder = apiContentRouteBuilder;
 
     protected override IApiContentResponse Create(IPublishedContent content, string name, IApiContentRoute route, IDictionary<string, object?> properties)
+    {
+        IDictionary<string, IApiContentRoute> cultures = GetCultures(content);
+        return new ApiContentResponse(content.Key, name, content.ContentType.Alias, content.CreateDate, content.UpdateDate, route, properties, cultures);
+    }
+
+    protected virtual IDictionary<string, IApiContentRoute> GetCultures(IPublishedContent content)
     {
         var routesByCulture = new Dictionary<string, IApiContentRoute>();
 
@@ -35,6 +40,6 @@ protected override IApiContentResponse Create(IPublishedContent content, string
             routesByCulture[publishedCultureInfo.Culture] = cultureRoute;
         }
 
-        return new ApiContentResponse(content.Key, name, content.ContentType.Alias, content.CreateDate, content.UpdateDate, route, properties, routesByCulture);
+        return routesByCulture;
     }
 }