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. 

return ProtocolServerAdapter(
                interserver_listen_host,
                port_name,
                "secure replica communication (interserver): https://" + address.toString(),
                std::make_unique<HTTPServer>(
                    context(),
                    createHandlerFactory(*this, async_metrics, "InterserverIOHTTPSHandler-factory"),
                    server_pool,
                    socket,
                    http_params));
#else
            UNUSED(port);
            throw Exception{"SSL support for TCP protocol is disabled because Poco library was built without NetSSL support.",
                            ErrorCodes::SUPPORT_IS_DISABLED};
#endif
        });
    }
}
void Server::updateServers(
    Poco::Util::AbstractConfiguration & config,
    Poco::ThreadPool & server_pool,
    AsynchronousMetrics & async_metrics,
    std::vector<ProtocolServerAdapter> & servers)
{
    Poco::Logger * log = &logger();
    const auto listen_hosts = getListenHosts(config);
    const auto interserver_listen_hosts = getInterserverListenHosts(config);
    const auto listen_try = getListenTry(config);
    
    auto check_server = [&log](const char prefix[], auto & server)