Bug 21503: Tests for the existing behavior

Bug 21503: Tests for the existing behavior

This patch introduces 7 tests for the current behaviour for the
AuthorisedValues template plugin.

To test:
- Apply this patch
- Run:
  $ kshell
 k$ prove t/db_dependent/Template/Plugin/AuthorisedValues.t
=> SUCCESS: Tests pass, all green!

Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>