NOBUG: Add upgrade notes

UPGRADING.md

@@ -6,6 +6,16 @@ More detailed information on key changes can be found in the [Developer update n
 
 The format of this change log follows the advice given at [Keep a CHANGELOG](https://keepachangelog.com).
 
+## 5.2dev
+
+### core_group
+
+#### Added
+
+- `groups_print_activity_menu()` and `groups_get_activity_group()` now include an additional `$participationonly` parameter, which is true by default. This can be set false when we want the user to be able to select a non-participation group within an activity, for example if a teacher wants to filter assignment submissions by non-participation groups. It should never be used when the menu is displayed to students, as this may allow them to participate using non-participation groups. Non-participation groups are labeled as such.
+
+  For more information see [MDL-81514](https://tracker.moodle.org/browse/MDL-81514)
+
 ## 5.1
 
 ### core

public/group/UPGRADING.md

@@ -0,0 +1,10 @@
+# core_group (subsystem) Upgrade notes
+
+## 5.2dev
+
+### Added
+
+- `groups_print_activity_menu()` and `groups_get_activity_group()` now include an additional `$participationonly` parameter, which is true by default. This can be set false when we want the user to be able to select a non-participation group within an activity, for example if a teacher wants to filter assignment submissions by non-participation groups. It should never be used when the menu is displayed to students, as this may allow them to participate using non-participation groups. Non-participation groups are labeled as such.
+
+  For more information see [MDL-81514](https://tracker.moodle.org/browse/MDL-81514)
+