Introduce `group_update` system hook for group renames and other group edits
The group_rename system hook doesn't send the hook when a group is renamed.
Steps to reproduce
- Create a new system hook.
- Create a new group.
- Rename newly created group to something else.
What is the current bug behavior?
When the group is renamed there is no system hook sent according to 'Recent Deliveries' section of the system hook.