Add groups permission as an available scope in oidc provider

[utix]

x_groups gives you the groups of an user but you don't know if it is an admin or a member

add x_groups_perm to add a _admin group for admin

{
  "sub": "admi.nistrateur.1942",
  "name": "Admi Nistrateur",
  "email": "admi.nistrateur@m4x.org",
  "study_years": [
    "X1942"
  ],
  "x_groups": [
    "1942",
    "Polytechnique.org",
    "X-Informatique"
  ],
  "x_groups_perm": [
    "1942",
    "Polytechnique.org",
    "Polytechnique.org_admin",
    "X-Informatique"
  ]
}

This allows to easily match groups with other tools