I can use all tuleap group features into gerrit
Complete story #2756

* When I create/switch binding => all members to gerrit group
* Add/Remove a user into parent ugroup => add/remove on all children user group that are on gerrit
* Remove binding => do nothing (gerrit group remains the same)

The Tuleap binded groups are replicated as Gerrit group of groups aka. included groups. This implies that, on gerrit side, we cannot take into account private projects or restricted users settings into account.
Given a "Developers" user group in Tuleap "Top Level" public project, And a "Developers" user group in Tuleap "Product" private project, bound to "Top Level/Developers", And "John", member of "Developers", "Top Level" project member but NOT "Product" project member, Then John doesn't have access to any content in "Product" Tuleap project, But he has access to Gerrit project that grant access to "Product/Developers" group While this scenario might sounds legit, the behaviours are different and should probably be documented.