code: public void addCachedChallenge(HttpUrl url, Map<String, String> challenge) {
          if (url == null || challenge == null) {
              return;
          }
          String authority = getAuthority(url);
          authority = authority.toLowerCase(Locale.ENGLISH);
          cachedChallenges.put(authority, challenge);
      }
docs: Uses authority to cache challenge.
  
  @param url
  the url that is used as a cache key.
  @param challenge
  the challenge to cache.