Store with Progress
storage_scu scu;
auto results = scu.store_batch(assoc, datasets,
[](size_t done, size_t total) {
std::cout << "Progress: " << done << "/" << total << "\n";
});
size_t succeeded = std::count_if(results.begin(), results.end(),
[](const auto& r) { return r.is_success(); });