A Batch is a collection of Shipments that you purchase and generate labels for together. Batches make it simpler to create shipping label for multiple shippings in just a few clicks.
When you first POST to create the Batch, we will send a webhook to your app that the Batch object is being created. ("state"= creating) It will take on average 1 minute to process 1,000 Shipments.
Once all are created, we will send another webhook to your application telling you it is complete ("state"= created). If there are any errors for the Batch object, we will tell you about them in the webhook ("state"= creation failed)
You can only get shipping labels for a Batch if all Shipments in the 'postage_purchased' status. If any of your purchases are failed, you should just remove that Shipment from the Batch during the previous step.