Bug 19784: Unit tests for /api/v1/patrons

Bug 19784: Unit tests for /api/v1/patrons

This patch adapts the existing endpoint's tests so they expect:
- 'patron_id' for 'borrowernumber'
- 'library_id' for 'branchcode'
- 'category_id' for 'categorycode'

In the process, I tried to make the tests more robust, by creating random
data that gets deleted to make sure our tests cases can't have false
positives.

Independent subtests are wrapped inside transactions to avoid
eventual interference.

To test:
- Apply the patch
- Run:
  $ kshell
 k$ prove t/db_dependent/api/v1/patrons.t
=> FAIL: The api doesn't implement the expected behaviour and attributes
for endpoint responses

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>