code: protected static <T extends ChallengeHandler> T create(Class<T> clazz) {
          return load0(clazz, ServiceLoader.load(clazz));
      }
docs: Creates a new instance of the sub-class of {@link ChallengeHandler} using
  the {@link ServiceLoader} API with the implementation specified under
  META-INF/services.
  
  @param T        sub-class of ChallengeHandler
  @param clazz    Class object of the sub-type
  @return ChallengeHandler