code: public HttpAuthServiceBuilder addOAuth2(Authorizer<? super OAuth2Token> authorizer, AsciiString header) {
          return addTokenAuthorizer(new OAuth2TokenExtractor(requireNonNull(header, "header")),
                                    requireNonNull(authorizer, "authorizer"));
      }
docs: Adds an OAuth2 {@link Authorizer} for the given {@code header}.