Add super admins and admins to notifications about stage changes.

Currently, notifications can only be sent to the owner or the assigned executive. The problem I see is that this floods the owner with notifications for every stage change, when notifying the assigned executive and the branch manager (super admin or admin) would be more than enough. Imagine me, as the owner, receiving notifications for every major stage change in every chat across 20 branches—that would be hundreds of notifications a day, impossible to read them all. I feel the best approach is for each branch manager to receive notifications about stage changes generated in their store, regardless of the assigned executive, and optionally the owner.