public ServerSetsRegistrationSpecBuilder additionalEndpoint(
            String name, Endpoint additionalEndpoint) {
        additionalEndpointsBuilder.put(requireNonNull(name, "name"),
                                       requireNonNull(additionalEndpoint, "additionalEndpoint"));
        return this;
    }
Adds the specified additional {@link Endpoint} with the specified {@code name}.
zookeeper3/src/main/java/com/linecorp/armeria/server/zookeeper/ServerSetsRegistrationSpecBuilder.java