private static String getFieldFromClass(Class<?> clazz, String fieldName) {
        try {
            return (String) clazz.getField(fieldName).get(null);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            throw new ConfigurationRuntimeException("No such field '" + fieldName + "' in class " + clazz + ", or could not access field.", e);
        }
    }
Comparison sort order: namespace, name, configId.
config/src/main/java/com/yahoo/vespa/config/ConfigKey.java