Somewhere between API resources, queue workers, repositories, clients and serializers there is a class of … classes/modules that does the needful. Gun-to-my-head, I would call them “services” but I’m looking for a less overloaded term. Maybe capabilities? Controllers? Pick a term from the business domain? What do you call them?
At their most general, they are “data processors.” In common parlance, they’re often called “algorithms,” although some folks insist that that is reserved for programs with trivial control flow. For disambiguation and comparison: