Spurious group membership change notifications

To add (or in theory, remove) users to a group, one needs to set the new complete list of members in a PUT call, as there is no PATCH support. The way this is implemented results in a notification being sent to every group member, saying that they have been removed from the group, and then that they have been added to the group, even though nothing really changed for them. I can see how this happens, with the code first removing everyone from the group and then re-adding from the new list, but it's not very nice.