post https://api.apicbase.com/api/v2/integrations/suppliers/files/
Creates an assortment file to be processed asynchronously.
If posting an assortment file with assortments and prices that are valid for multiple customers, then all customers would have the same customer_number (and in this sense the customer number here works more like an "assortment ID").
The file uploaded here is a JSON file that needs to follow a specific format. Consult the guide for details.