Align Event Start/End send parameter for notification subscribers of the same group

Currently, when a group is added as a subscriber to a notification rule template, all the group members are added with the parameter "Event Start". They can be individually customized.

When all group members have been set to "Event End" and a new subscriber is added to a group, it still takes the parameter "Event Start" in all notifications of this group, and this requires being changed one by one.

=> in most cases on our side, there is no reason why subscribers of the same group would require receiving the notification at different times. We would be interested to get an option ON/OFF for forcing this parameter Start/End/Start&End at the group level, rather than every individual subscriber.