code: public static Credentials digestCredentials(String username, String password) {
      MorePreconditions.checkNotBlank(username);
      Objects.requireNonNull(password);
  
      // TODO(John Sirois): DigestAuthenticationProvider is broken - uses platform default charset
      // (on server) and so we just have to hope here that clients are deployed in compatible jvms.
      // Consider writing and installing a version of DigestAuthenticationProvider that controls its
      // Charset explicitly.
      return credentials("digest", (username + ":" + password).getBytes());
    }
docs: Creates a set of credentials for the zoo keeper digest authentication mechanism.
  
  @param username the username to authenticate with
  @param password the password to authenticate with
  @return a set of credentials that can be used to authenticate the zoo keeper client