I agree, it's better to use borrowernumber for the cache key and I also
take the oportunity to rename it to more clearly reflect the function
(it's no longer 'login' only, it's now 'activity')
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>