Bug 23634: Prevent non-superlibrarians from editing superlibarian emails

Bug 23634: Prevent non-superlibrarians from editing superlibarian emails

This patchset prevents a non-superlibrarian user from editing a
superlibrarians email address via memberentry.  This is to prevent a
privilege escalation vulnerability whereby a user could update a
superlibrarians contact details to match their own and then request a
password reset via the OPAC.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>