for my need it's ok to manage schedule hiding all personal data for normal users:
$conf['app']['privacyMode'] = 1;
With the above configuration only admin can invite users to a participation.
Anyway I would like to do something extra:
1) User profiles should have a new field: "Allow other group users to invite you".
2) Users from same group should have to be able to invite each other.
3) Users from same group should have to be able to see data of their participation/invitation.
So, users of the same group, who accept to be invited, could see and invite each other.
Could you give me a hint to realize it?