Allow out of hours bookings to people who have access

[johnmckerrell]

I nearly added this as "restrict out of hours" but given that we're already doing that by having reduced time slots I thought I'd switch it around. In the future, when we actually have a user database that can record things like whether you have out of hours access, we should be able to mark some slots as "out of hours" or "requires extended access" or something like that. Probably if you came to Optimism without signing in at all these slots would not be visible but there would be some text on the page along the lines of "If you want to see out of hours slots then log in".

AC:

• When not logged in, the calendar UI looks the same but has text on the bottom suggesting I log in for more slots
• When logged in, if I don't have out of hours access then further text suggests I sign up for it?
• When logged in and I have access, I can see and book more slots