We also support the DHL tracking workflow now

Unlike most shipping providers, DHL requires the order to be marked as shipped before it adds the tracking details to the order in Shopify.

This meant Shopify sent us a fulfillment webhook with no tracking information yet, and Market Sync would mark the order as shipped without a tracking code.

To fix this, we now wait a few minutes before syncing the tracking details, giving DHL time to fill in the shipment data first.