text: --
  --
  -- Forbidding gaps (and overlaps):
  --
  --
  SELECT  room_id, range_agg(booked_during, false)
  FROM    reservations
  WHERE   room_id = 1
  GROUP BY room_id;
  
  SELECT  room_id, range_agg(booked_during, false)
  FROM    reservations
  WHERE   room_id = 6
  GROUP BY room_id;
  
  SELECT  room_id, range_agg(booked_during, false)
  FROM    reservations
  WHERE   room_id NOT IN (1, 6)
  GROUP BY room_id;
  --
  --
  -- Permitting gaps (but forbidding overlaps):
  --
  --
  SELECT  room_id, range_agg(booked_during, true)
  FROM    reservations
  WHERE   room_id = 1
  GROUP BY room_id;
  
  SELECT  room_id, range_agg(booked_during, true)
  FROM    reservations
  WHERE   room_id = 6
  GROUP BY room_id;
  
  SELECT  room_id, range_agg(booked_during, true)
  FROM    reservations
  WHERE   room_id NOT IN (1, 6)
  GROUP BY room_id;
  