Add option for no Authentication

[KoEnix]

Hi,

thanks again for the nice work of increasing the download functionality ^^.
Would it be possible to implement an option for a "non-authentication", e.g. when CoTurn is used with default settings, without any credentials?

If I read the config-file of CoTurn correctly, by default no authentication is in place.
https://github.com/coturn/coturn/blob/master/docker/coturn/turnserver.conf

Thanks a log ^^

[livy111]

Bump