improved

REST API: `customerUserAgent` field for orders

We added a new order field to REST API: customerUserAgent. The field contains information about the customer's device and browser used to place an order. It is read-only and uses User-Agent header format.

If an order doesn't have the field, Ecwid didn't recognize the customer's device, or an order was placed with REST API.

The new field is available in the following endpoints: