ConfigTracker::EntryOwnerPtr ConfigTrackerImpl::add(const std::string& key, Cb cb) {

  auto insert_result = map_->emplace(key, std::move(cb));

  return insert_result.second

             ? std::make_unique<ConfigTrackerImpl::EntryOwnerImpl>(map_, std::move(key))

             : nullptr;

}

const ConfigTracker::CbsMap& ConfigTrackerImpl::getCallbacksMap() const { return *map_; }

    : map_(map), key_(key) {}

ConfigTrackerImpl::EntryOwnerImpl::~EntryOwnerImpl() {

  size_t erased = map_->erase(key_);

  ASSERT(erased == 1);

}