Improve the flight Graph schema

[denironyx]

We want to review flight schema.. I think we should include data source and change type -> source

fn,
    type='Flight',
    year=int(r['year']),
    month=int(r['month']),
    day=int(r['day']),
    carrier=r['carrier'],
    flight_number=r['flight'],
    tail_number=r.get('tail_number', None),
    origin=r['origin'],
    dest=r['dest'],
    cancelled=bool(r['cancelled']),
    delayed=bool(r['delayed'])