private static void setConfigId(ConfigInstance instance, String configId)
            throws NoSuchFieldException, IllegalAccessException {
        Field configIdField = ConfigInstance.class.getDeclaredField("configId");
        configIdField.setAccessible(true);
        configIdField.set(instance, configId);
        configIdField.setAccessible(false);
    }
Copies all values that have been explicitly set on the source to the destination.
Values that have not been explicitly set in the source builder, will be left unchanged
in the destination.

@param destination the builder to copy values into
@param source the builder to copy values from. Unset values are not copied
@param <BUILDER> the builder class
config/src/main/java/com/yahoo/config/subscription/ConfigInstanceUtil.java