Bug 22144: (QA follow-up) Prepare the ground for other formats

Bug 22144: (QA follow-up) Prepare the ground for other formats

This patch refactors the original implementation so it is ready for
supporting other formats. It also adds some error handling.

To test:
- Apply this patch
- Run:
  $ kshell
 k$ prove t/db_dependent/Koha/Biblio/Metadata.t
=> SUCCESS: Tests pass!
- Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>