post https://admin.sandbox.vouchery.app/api/v2.1/campaigns//vouchers/batch-by-customer-categories
Generate a batch of unique vouchers for all customers in given categories. Each voucher will be created using {prefix}{random code} format where code will be a random string of requested type and length. A prefix needs to be unique within a project.
Following code types are supported:
digits
letters
mixed (digits and letters)
Allowed characters for each code type have been filtered to avoid typing mistakes.