Elaborate CHANGELOG

CHANGELOG.md

@@ -1,7 +1,33 @@
 ## vNext (TBD)
 
 ### Breaking changes
-* The generated parts are now named `.realm.dart` instead of `.g.dart`. This is because the builder is now a `PartBuilder`, instead of a `SharedPartBuilder`. This implies that other builders can consume the output.
+* The generated parts are now named `.realm.dart` instead of `.g.dart`. This is because the builder is now a `PartBuilder`, instead of a `SharedPartBuilder`. To migrate to this version you need to update all the part declarations to match, ie. `part 'x.g.dart` becomes `part x.realm.dart` and rerun the generator.
+
+  This makes it easier to combine builders. Here is an example of combining with `dart_mappable`:
+  ```dart
+  import 'package:dart_mappable/dart_mappable.dart';
+  import 'package:realm_dart/realm.dart';
+
+  part 'part_builder.realm.dart';
+  part 'part_builder.mapper.dart';
+
+  @MappableClass()
+  @RealmModel()
+  class $Stuff with $StuffMappable {
+    @MappableField()
+    late int id;
+
+    @override
+    String toString() => 'Stuff{id: $id}';
+  }
+
+  final realm = Realm(Configuration.local([Stuff.schema]));
+  void main(List<String> arguments) {
+    final s = realm.write(() => realm.add(Stuff(1), update: true));
+    print(s.toJson()); // <-- realm object as json
+    Realm.shutdown();
+  }
+  ```
 
 ### Enhancements
 * None

packages/realm_dart/lib/src/native/realm_core.dart

@@ -1735,7 +1735,7 @@ class _RealmCore {
     }
   }
 
-  static void user_change_callback(Pointer<Void> userdata, int data) {
+  static void user_change_callback(Object userdata, int data) {
     final controller = userdata as UserNotificationsController;
 
     controller.onUserChanged();