Gets a list of group or project members viewable by the authenticated user, including inherited members through ancestor groups.
When a user is a member of the project/group and of one or more ancestor groups the user is returned only once with the project `access_level` (if exists)
or the `access_level` for the user in the first group which he belongs to in the project groups ancestors chain.
or the `access_level` for the user in the first group which they belong to in the project groups ancestors chain.