contrib: minor CERN plugin fix
contrib: minor CERN plugin fix

* Fixes an issue where `g.identity.provides` was populated with
  only the Cern groups. As access rights can be assigned to single
  users (i.e. emails), the user's e-mail must also be included in the
  `g.identity.provides`.

* NOTE Appends '@cern.ch' to every CERN group, for uniform formatting.

Signed-off-by: Orestis Melkonian <a8803610f79fcd815ba94c447e9ee72ed88af885@gmail.com>

tiborsimko/invenio-oauthclient,inveniosoftware/invenio-oauthclient,inveniosoftware/invenio-oauthclient,tiborsimko/invenio-oauthclient,inveniosoftware/invenio-oauthclient,tiborsimko/invenio-oauthclient