Function find

3rd/nlohmann_json/include/nlohmann/json.hpp:4526–4536

    */
    template<typename KeyT>
    iterator find(KeyT&& key)
    {
        auto result = end();

        if (is_object())
        {
            result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
        }

        return result;
    }

    /*!
    @brief find an element in a JSON object