Method has_next

test-app/runtime/src/main/cpp/ada/ada.h:8897–8899

template <typename T, url_search_params_iter_type Type>
inline bool url_search_params_iter<T, Type>::has_next() const {
  return pos < params.params.size();
}

template <>
inline std::optional<std::string_view> url_search_params_keys_iter::next() {