Bug 29185: Groundwork: add template GetCnumSearchURL in Utils

Bug 29185: Groundwork: add template GetCnumSearchURL in Utils

Note for QA: Opened bug 33515 to see if we can use this same
function in a few other places too. Would probably reduce code
and increase consistency.

Test plan:
See next patch.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>