V15: Add authorization to saves (#18111)

* Re-add authorization

* Add test plumbing

* Add test helper

* Add happy path test

* Remove usage of negation

* Minor DRYup of test code.

---------

Co-authored-by: Andy Butland <abutland73@gmail.com>

tests/Umbraco.Tests.Common/TestHelpers/DocumentUpdateHelper.cs

@@ -0,0 +1,31 @@
+using Umbraco.Cms.Api.Management.ViewModels;
+using Umbraco.Cms.Api.Management.ViewModels.Document;
+using Umbraco.Cms.Core.Models.ContentEditing;
+
+namespace Umbraco.Cms.Tests.Common.TestHelpers;
+
+public static class DocumentUpdateHelper
+{
+    public static UpdateDocumentRequestModel CreateInvariantDocumentUpdateRequestModel(ContentCreateModel createModel)
+    {
+        var updateRequestModel = new UpdateDocumentRequestModel();
+
+        updateRequestModel.Template = ReferenceByIdModel.ReferenceOrNull(createModel.TemplateKey);
+        updateRequestModel.Variants =
+        [
+            new DocumentVariantRequestModel
+            {
+                Segment = null,
+                Culture = null,
+                Name = createModel.InvariantName!,
+            }
+        ];
+        updateRequestModel.Values = createModel.InvariantProperties.Select(x => new DocumentValueModel
+        {
+            Alias = x.Alias,
+            Value = x.Value,
+        });
+
+        return updateRequestModel;
+    }
+}