Added endpoints for Order and Customer imports

The Import API now supports two additional resource types, Orders and Customers.

To create or update bulk Orders in the commercetools platform, use the Importing Orders endpoint. This new feature calls platform endpoints such as Create an Order by Import for creating new orders and Update Order for updating existing orders.

To create or update customers in bulk in the commercetools platform, use Importing Customers endpoint. This new feature calls platform endpoints such as Create Customer for creating new cutomers and Update Customer for updating existing cutomers.

The new feature includes the following changes.

Orders import:

• New endpoint for Order import Request Order data to be imported.
• New endpoint for querying the status of Order ImportOperations by an ImportSink key Get ImportOperations by an ImportSink key.
• New endpoint for querying the status of Order ImportOperations by its id Get Import operation by its ID.

Customers import:

• New endpoint for Customer import Request customer data to be imported.
• New endpoint for querying the status of Customer ImportOperations by an ImportSink key Get ImportOperations by an ImportSink Key.
• New endpoint for querying the status of Customer ImportOperation by its id Get ImportOperation by its ID.