Bug 35106: Validate entered borrowernumber and biblio_id

Bug 35106: Validate entered borrowernumber and biblio_id

Following up from the test plan of the previous patch:
1) Edit the request again, input gibberish in the Patron ID e.g. 'asdasd'
2) Hit 'Submit'
3) Notice you get a 'The Patron ID you entered is invalid.' message.
4) Edit again, try to empty the input on the Patron ID, hit 'Submit'.
5) Notice it saves the patron as null, as expected

Repeat the test plan, but now for the Bibliographic record ID, notice
the message 'The Bibliographic record ID you entered is invalid.' is
shown if a no biblio was found.

Signed-off-by: David Nind <david@davidnind.com>
squash this

Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>