Bug 14048: Unit tests

Bug 14048: Unit tests

This patch introduces unit tests for the feature.
To test:
- Have all patches from this bug applied
- Run:
  $ prove -v t/db_dependent/RefundLostItemFeeRule.t
=> SUCCESS: All tests pass!

Sponsored-by: DoverNet
Sponsored-by: South-East Kansas Library System
Sponsored-by: SWITCH Library Consortium
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jason Robb <jrobb@sekls.org>
Signed-off-by: Jennifer Schmidt <jschmidt@switchinc.org>
Signed-off-by: Margaret Thrasher <p.thrasher@dover.nh.gov>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jesse Weaver <jweaver@bywatersolutions.com>