Ability to ignore certain Booker bookings

Many bookings have been imported in to Booker staging by Becky or a 'Student Registry' user.

Currently all bookings are either 3rd party bookings that need to be synced to roombookings in TermTime, or treated as event previously synced from TermTime by the essm-sync user. These imported bookings are neither.

Add the option for an booker.ignore_bookings configuration option. Flexibility could be added to filter on more than just BookedBy.Id.

Possibly:

booker:
   ignore_bookings:
      - by: bookedby
        ids:
           - list
           - of
           - users
      - by: room
        id: "or single id"

with a limited (just booked by, room and building to start with?) set of by options and either id or ids with their values.