Changes to Get Coupon

the response property allowed_emails became nullable for the status 200

the response property expiration_date became nullable for the status 200

the response property max_uses became nullable for the status 200

the response property max_uses_per_customer became nullable for the status 200

the response property min_invoice_price became nullable for the status 200

the response property payment_method_ids became nullable for the status 200

the response property start_date became nullable for the status 200

added the optional property disable_if_reseller_discount to the response with the 200 status