subscribeAndUnwrap(to:onNext:onComplete:)

@discardableResult @preconcurrency func subscribeAndUnwrap<Service, Instance>(to service: Service, onNext nextResultHandler: @escaping (Result<[Instance], Error>) -> Void, onComplete completionHandler: @escaping (CompletionReason) -> Void = { _ in }) -> CancellationToken where Service : Hashable, Service : Sendable, Instance : Hashable, Instance : Sendable