Bug 30133: Simplify code

Bug 30133: Simplify code

This patch simplifies the code, and also fixes a problem with branchcode
comparisson failing, highlighted when running the tests

To test:
1. Apply the regression tests
2. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/items.t
=> FAIL: Tests fail. Notably:
- Link header pagination is wrong
- X-*Total-Count headers have two values (dupicated)
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass!
5. Sign off :-D

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>