Merge pull request #6648 from umbraco/15/somebreaking

Add Trimstart/end notes

Author: sofietoft

15/umbraco-cms/fundamentals/setup/upgrading/version-specific/README.md

@@ -21,11 +21,16 @@ Use the [general upgrade guide](../) to complete the upgrade of your project.
 
 <summary>Umbraco 15</summary>
 
-* **Snapshots are removed**
+**`TrimStart` & `TrimEnd`**
+
+The string extension methods `TrimStart` and `TrimEnd` are implemented natively in .NET 9 and behave differently from the ones used by Umbraco.
+Due to this, the Umbraco versions have changed names. Use `TrimStartExact` and `TrimEndExact` instead.
+
+**Snapshots are removed**
 
 Snapshots have been removed, meaning any code using `IPublishedSnapshot`, and by extension `IPublishedSnapshotAccessor`, must be updated. Inject `IPublishedContentCache` or `IPublishedMediaCache` and use those directly instead.
 
-* **Modelsbuilder models needs to be rebuilt**
+**Modelsbuilder models needs to be rebuilt**
 
 Models generated by ModelsBuilder used the `IPublishedSnapshot` interface, which has been removed. This means that the models need to be rebuilt. The approach to this will differ depending on the mode chosen: