Non-persistent sessions? session_options?

How can I set my Rails sessions to not be persistent accross browser
restarts? That, the cookies involved with sessions/session tokens
should be set to have an empty “expires” attribute, I think.

It looks like maybe the method session_options is what you might use for
this, but I can’t figure out where, if anywhere, the meaningful keys to
the session_options hash are documented.

Any hints?