As a team admin, I want to get en email notification when a user is added or removed from my team

Problem Definition

In an individual Bitbucket account, only the account owner can add users to the account's user groups.
However, in a team, there may be multiple admins who are able to add users, and they would like to be notified when other admins add/remove users to the team.

Suggested Solution

Allow users to enable/disable email notifications when users are added/removed from teams they administer