Admin need to be able to list only their participations

[RignonNoel]

Expected behavior

When i'm an administrator (ie: staff) i want to be able to do a GET /participations and having only my participations

Current behavior

By default all the participations are returned, and no filter are available.

Potential solution

Adding a new Django filter user to filter participations by user

Step to reproduce (if it's a bug)

1. Create 2 reservation on two differents admin user
2. Do a call on GET /participations
3. Try to play with filters available to find only your reservations