Restructure breaking changes for 4.0 in changelog

CHANGELOG.rst

@@ -11,13 +11,6 @@ and this project adheres to `Semantic Versioning`_.
 
 Notable, breaking changes
 ~~~~~~~~~~~~~~~~~~~~~~~~~
-The "managed models" feature is mandatory for all models derived from `ExtensibleModel`
-and requires creating a migration for all downstream models to add the respective field.
-
-The "additional fields" feature has been removed because it had design issues
-that practically made it unusable in all scenarios. No migration path away
-from the feature is defined. If you have been using additional group fields
-and need a replacement, please contact the development team.
 
 The special assignment page for groups and child groups has been removed.
 
@@ -28,14 +21,28 @@ for PostgreSQL.
 AlekSIS now uses Valkey as a drop-in replacement for Redis. Please update your configuration
 files accordingly (see docs for further instructions).
 
-As legacy pages are no longer themed, you should update them to the new frontend as soon as possible.
-
 To make setting names consistent, the setting ``auth.login.registration.unique_email``
 was renamed to ``auth.registration.unique_email``.
 
+The "additional fields" feature has been removed because it had design issues
+that practically made it unusable in all scenarios. No migration path away
+from the feature is defined. If you have been using additional group fields
+and need a replacement, please contact the development team.
+
+The "managed models" feature is mandatory for all models derived from `ExtensibleModel`
+and requires creating a migration for all downstream models to add the respective field.
+
+As legacy pages are no longer themed, you should update them to the new frontend as soon as possible.
+
 To prevent collisions with fields, the class variable ``name`` on ``RegistryObject`` has been renamed
 to ``_class_name``. Please update any references and subclasses.
 
+Deprecated
+~~~~~~~~~~
+
+* The field ``owners`` of group will be removed in the next release and will be replaced by memberships
+  using the special ownership role.
+
 Added
 ~~~~~