Support protecting joining a room by login

[jmattheis]

#103 (comment)

To prevent a breaking config change, I think a new setting like SCREEGO_REQUIRE_LOGIN_ON=create / SCREEGO_REQUIRE_LOGIN_ON=create-and-login should be added.

[wangdemon]

This idea is very good. I hope the author can complete this function.

[R-Jeske]

I would like to have a simple one time password for a session. This is enough for most usecases.