Shape compact receipts

`$project` defines the document shape that leaves a stage. Use it to include fields, exclude `_id`, or rename values with field paths.

Return `orderId`, `customerId`, and `total` only. Rename `_id` to `orderId`.

Expected result: 12 documents with exactly three fields.

[
  { $project: { customerId: 1, total: 1 } }
]