code: @Nonnull
      protected JSONSignatureValidator getJsonSignatureValidator(@CheckForNull String name) {
          if (name == null) {
              name = signatureValidatorPrefix + " '" + id + "'";
          }
          return new JSONSignatureValidator(name);
      }
docs: Let sub-classes of UpdateSite provide their own signature validator.
  @param name, the name for the JSON signature Validator object.
  if name is null, then the default name will be used,
  which is "update site" followed by the update site id
  @return the signature validator.
  @since 2.21