Bug 35929: Don't record a change for empty fields submitted in patron form

Bug 35929: Don't record a change for empty fields submitted in patron form

This is reminiscent of bug 36159 - when a field is submitted as empty, and null in the DB
we need to reject this as a change. I tried to copy the logic from that bug, as well as
deleting submitted changes for hidden fields (from html manipulation)

This should be tested extensively. One note: If you submit a valid change request, then submit a second with no change the second will be ignored, but the first will remain. i.e. if you change your name from 'Nick' to 'Nack' - then realize your typo you cannot submit a new request to change it back untl the initial request is cleared

To test:
1 - Play with PatronSelfModificationBorrowerUnwantedField and PatronSelfModificationMandatory field to have some fields set
2 - Add a patron attribute, or several, that are editable in the OPAC
3 - Try submitting a form with no changes, note a modification requets is submitted
4 - Approve the request
5 - Apply patch, restart all
6 - Try submitted a blank request, you are notified there were no changes
7 - Try to force an unwanted field via html modification
8 - No changes reported
9 - Confirm attributes changes are successful
10 - After a successful request, try submitting a blank request
11 - Note no changes are recorded, but the initial request is still active

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>