Bug 23843 introduced the Koha::Object(s)->to_api method and the attribute mappings on the Koha::Object classes. Bug 23893 will introduce the reverse mapping along with the Koha::Object->new_from_api and Koha::Object->set_from_api methods. So all the pieces are set so we can properly build a Koha::Objects->search_from_api method that does something similar to the objects.search helper, but uses the classes' mappings instead of requiring the to_api and to_model methods to be passed. This will ultimately help clean all the controllers and (hopefully) improve productivity re: adding endpoints, because of the removal of that intrinsic complexity both on controllers, and tests.
Im' closing this, as things evolved in a nicer way, at the right level (in the controller space).