input: Write a python function to handle order processing in a Flask route.
  assert order({'customer_id': 123, 'items': ['item1', 'item2']}) == {'message': 'Order processed'}
  assert order({'customer_id': 456, 'items': ['item3', 'item4']}) == {'message': 'Order processed'}
  assert order({'customer_id': 789, 'items': ['item5', 'item6']}) == {'message': 'Order processed'}
output: def order(data):
      customer_id = data.get('customer_id')
      items = data.get('items')
      
      if customer_id and items:
          # Here we would add logic to process the order, such as saving to a database, etc.
          return {'message': 'Order processed'}
      else:
          return {'message': 'Invalid order'}