For breakout sessions, allow specification of a preferred day #292
Description
When we have breakouts on multiple days, sometimes people express a preferred day. Ideally the scheduler would allow us to constrain scheduling of a session to a particular day, would try to schedule first those sessions with that constraint, and if it's unable to schedule the session on that day, issue a warning but schedule it on another day.
One idea for this is an additional Day column in the spreadsheet (sparsely filled out since we only get a few requests for specific days).