code: public HttpAuthServiceBuilder addOAuth1a(Authorizer<? super OAuth1aToken> authorizer, AsciiString header) {
          return addTokenAuthorizer(new OAuth1aTokenExtractor(requireNonNull(header, "header")),
                                    requireNonNull(authorizer, "authorizer"));
      }
docs: Adds an OAuth1a {@link Authorizer} for the given {@code header}.