interface Request {

        String asString();
    }

    class MultipleUserRequest implements Request {
        private final List<Username> usernames;

        @Inject
        public MultipleUserRequest(List<Username> usernames) {
            this.usernames = usernames;
        }

        @Override
        public String asString() {
            return usernames.stream().map(Username::asString).collect(Collectors.joining(",", "[", "]"));
        }
    }

    class AllUsersRequest implements Request {
        @Override
        public String asString() {
            return "[]";
        }
    }

class InVMDisconnectorNotifier implements DisconnectorNotifier {
        private final Disconnector disconnector;

        @Inject
        public InVMDisconnectorNotifier(Disconnector disconnector) {
            this.disconnector = disconnector;
        }

        @Override
        public void disconnect(Request request) {
            switch (request) {
                case MultipleUserRequest multipleUserRequest:
                    disconnector.disconnect(multipleUserRequest.usernames::contains);
                    break;
                case AllUsersRequest allUsersRequest:
                    disconnector.disconnect(username -> true);
                    break;
                default:
                    throw new IllegalStateException("Unexpected value: " + request);
            }
        }
    }

class RabbitMQDisconnectorNotifier implements DisconnectorNotifier {
        private final reactor.rabbitmq.Sender sender

        @Override
        public void disconnect(Request request) {
            sender.send(request.asString()....)
        }
    }