Automatically lock all roles at a certain time

To avoid no surprise sign ups, allow to set when the party automatically locks all roles. As default, all roles will lock when the party starts, but can be changed to any arbitrary relative time to when the party starts (e.g. “15 minutes before”, “24 hours before”, “5 minutes after”). This can also be toggled off, if the party allows drop in sign ups, but is toggled on by default.