Ordinary database engine is deprecated but there is no simple mean to change database engine to Atomic for existing databases.

Possible options:
- ALTER DATABASE MODIFY ENGINE query.
- Flag that triggers migration at ClickHouse startup.

The latter should be easier to implement. 

skip_sanity_checks = true;
            current_zookeeper->remove(replica_path + "/flags/force_restore_data");
            LOG_WARNING(log, "Skipping the limits on severity of changes to data parts and columns (flag {}/flags/force_restore_data).", replica_path);
        }
        else if (has_force_restore_data_flag)
        {
            skip_sanity_checks = true;
            LOG_WARNING(log, "Skipping the limits on severity of changes to data parts and columns (flag force_restore_data).");
        }
    }
    loadDataParts(skip_sanity_checks);
    if (!current_zookeeper)
    {
        if (!attach)
        {
            dropIfEmpty();
            throw Exception("Can't create replicated table without ZooKeeper", ErrorCodes::NO_ZOOKEEPER);
        }
        
        LOG_ERROR(log, "No ZooKeeper: table will be in readonly mode.");
        has_metadata_in_zookeeper = std::nullopt;
        return;
    }
    if (attach && !current_zookeeper->exists(zookeeper_path + "/metadata"))
    {
        LOG_WARNING(log, "No metadata in ZooKeeper for {}: table will be in readonly mode.", zookeeper_path);
        has_metadata_in_zookeeper = false;
        return;
    }
    auto metadata_snapshot = getInMemoryMetadataPtr();