Auto-register Airtable shipments in AfterShip with ETAs

When ops drops a new row into our Airtable shipments queue, register the tracking in AfterShip and stamp the predicted delivery date back on the row.

Trigger: poll on new Airtable records in the shipments table. The row carries the tracking number, an optional courier slug field, destination postal code, customer contact (name + email), origin location, pickup date, and empty writeback columns for the AfterShip tracking id, detected courier slug, predicted delivery date, and a status/failure-reason column.

For each new row: if the courier slug field is blank, call AfterShip Detect Courier with the tracking number to identify the carrier. Then call AfterShip Create Tracking with the tracking number, courier slug (detected or provided), destination postal code, and customer contact. Then call AfterShip Predict Estimated Delivery Date using the origin, destination, and pickup date from the row. Finally, write the AfterShip tracking id, the detected/confirmed courier slug, and the predicted delivery date back to the Airtable row via Update Record.

Skip rows that already have an AfterShip tracking id filled in so we never register the same shipment twice.

Error handling is per-row and must never fail the whole run. If a row can't be resolved (Detect Courier returns nothing or is ambiguous, a required field is missing, or AfterShip rejects the tracking number), do not throw. Instead, use Airtable Update Record to stamp a plain-language reason on the status column ("couldn't detect courier", "missing destination postal code", "tracking number rejected by AfterShip") so ops can fix and re-run rather than silently failing. Continue to the next row.