When a CERN user who is not in the appropriate e-group (e.g. the one for shifters) logs in, they have Guest privileges and only a blank home page is shown. Add a message notifying them about missing permissions.

Note: for the training instance, Guests could be granted access to all features of Certhelper.
When a CERN user who is not in the appropriate e-group (e.g. the one for shifters) logs in, they have
Guestprivileges and only a blank home page is shown. Add a message notifying them about missing permissions.Note: for the
traininginstance,Guests could be granted access to all features of Certhelper.