Bug 35757: Fix unit tests for external counter registry API

Bug 35757: Fix unit tests for external counter registry API

This patch updates the unit tests for the external counter registry API used in the Usage Statistics module. The intent of the tests is to identify any changes in the external response that could lead to errors in Koha. To do this, the tests now compare the list of hash keys returned in the response with the current definition in Koha, and identifies any new fields that need to be added to the definition.

Test plan:
prove t/db_dependent/api/v1/erm_counter_registries.t
prove t/db_dependent/api/v1/erm_sushi_services.t

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>