New backoffice/add system text json configuration attribute (#12998)

* Add SystemTextJsonConfigurationAttribute

* Fix up formatting

* Rename classes for clearer purpose

Co-authored-by: Zeegaan <nge@umbraco.dk>

src/Umbraco.Cms.ManagementApi/Controllers/ManagementApiControllerBase.cs

@@ -0,0 +1,10 @@
+using Microsoft.AspNetCore.Mvc;
+using Umbraco.Cms.ManagementApi.Filters;
+
+namespace Umbraco.Cms.ManagementApi.Controllers;
+
+[ManagementApiJsonConfiguration]
+public class ManagementApiControllerBase : Controller
+{
+
+}

src/Umbraco.Cms.ManagementApi/Filters/ManagementApiJsonConfigurationAttribute.cs

@@ -0,0 +1,33 @@
+using System.Text.Json;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Filters;
+
+namespace Umbraco.Cms.ManagementApi.Filters;
+
+public class ManagementApiJsonConfigurationAttribute : TypeFilterAttribute
+{
+    public ManagementApiJsonConfigurationAttribute() : base(typeof(SystemTextJsonConfigurationFilter)) =>
+        Order = 1; // Must be low, to be overridden by other custom formatters, but higher then all framework stuff.
+
+    private class SystemTextJsonConfigurationFilter : IResultFilter
+    {
+        public void OnResultExecuted(ResultExecutedContext context)
+        {
+        }
+
+        public void OnResultExecuting(ResultExecutingContext context)
+        {
+            if (context.Result is ObjectResult objectResult)
+            {
+                var serializerOptions = new JsonSerializerOptions
+                {
+                    PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+                };
+                objectResult.Formatters.Clear();
+                objectResult.Formatters.Add(new ManagementApiJsonOutputFormatter(serializerOptions));
+            }
+        }
+    }
+}
+
+

src/Umbraco.Cms.ManagementApi/Filters/ManagementApiJsonOutputFormatter.cs

@@ -0,0 +1,19 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.AspNetCore.Mvc.Formatters;
+
+namespace Umbraco.Cms.ManagementApi.Filters;
+
+public class ManagementApiJsonOutputFormatter : SystemTextJsonOutputFormatter
+{
+    public ManagementApiJsonOutputFormatter(JsonSerializerOptions jsonSerializerOptions) : base(RegisterJsonConverters(jsonSerializerOptions))
+    {
+    }
+
+    protected static JsonSerializerOptions RegisterJsonConverters(JsonSerializerOptions serializerOptions)
+    {
+        serializerOptions.Converters.Add(new JsonStringEnumConverter());
+
+        return serializerOptions;
+    }
+}