Allow groups members to see other members for some groups

[armanddidierjean]

Subject of the issue

For some groups (ex: admin, or other association groups) we could allow a member to see the list of other members. This would allow someone to check that unauthorized people are not in the group, and thus don't have access to sensible data.

We could consider sending a notification to group members when someone is added or deleted for the group.

We can't allow that for all groups, as Account Types like student or massive groups like ae, to prevent someone to scrape a massive part of our users.