V15: Fix webhook RTE serialization (#17656)

* Make base type resolver class

* Add new webhook serializer

* fix comment

* Update src/Umbraco.Infrastructure/Serialization/ContentJsonTypeResolverBase.cs

Co-authored-by: Elitsa Marinovska <21998037+elit0451@users.noreply.github.com>

* Update src/Umbraco.Core/Services/WebhookRequestService.cs

---------

Co-authored-by: Elitsa <elm@umbraco.dk>
Co-authored-by: Elitsa Marinovska <21998037+elit0451@users.noreply.github.com>

src/Umbraco.Infrastructure/Serialization/SystemTextWebhookJsonSerializer.cs

@@ -0,0 +1,31 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Umbraco.Cms.Core.Serialization;
+
+namespace Umbraco.Cms.Infrastructure.Serialization;
+
+/// <inheritdoc />
+public sealed class SystemTextWebhookJsonSerializer : SystemTextJsonSerializerBase, IWebhookJsonSerializer
+{
+    private readonly JsonSerializerOptions _jsonSerializerOptions;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SystemTextWebhookJsonSerializer" /> class.
+    /// </summary>
+    public SystemTextWebhookJsonSerializer()
+        => _jsonSerializerOptions = new JsonSerializerOptions()
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+            Converters =
+            {
+                new JsonStringEnumConverter(),
+                new JsonUdiConverter(),
+                new JsonUdiRangeConverter(),
+                new JsonObjectConverter(), // Required for block editor values
+                new JsonBlockValueConverter()
+            },
+            TypeInfoResolver = new WebhookJsonTypeResolver(),
+        };
+
+    protected override JsonSerializerOptions JsonSerializerOptions => _jsonSerializerOptions;
+}