The class manager should see the statistics page

If a class manager manages classes part of one or more learning paths, they should be able to see statistics related to those learning paths.

Particularly:

Visiting /statistics/dashboard they should be able to see the statistics of the learning paths where the classes they are managing are part of
If none of the classes they are managing are "member" of any learning path, they should receive 403 when accessing /statistics/dashboard (current behavior)
On the bottom of the page, the list will only contain the learning paths where they managed classes are members.
When the class manager clicks "Details" on each row, it should see the training statistics