Create Discounts Via API

Hello Team, 

Our use case:
1. A restaurant defines an offer in our portal, for example $5 off the check or $3 off specific items.
2. The offer exists as a discount in the restaurant's Toast account, so staff can apply it at the till.
3. A  member shows a QR code in the cafe and the cashier scans it to apply the discount.
4. Redemptions are reported back to the restaurant and to our portal.

We only apply discounts and don't handle payments.

Questions:
1. Is there any API or tool for creating or updating discounts and promo codes, including a bulk import? If so, which integration type and access level does it require?
2. If not, what is the recommended way for an integration to apply discounts at the till without per-restaurant manual setup: the Loyalty Integration, the Promotions Integration, the Tender integration, or a Custom integration?
3. Is a feature request for a create/update discounts endpoint something we can submit, and is anything similar planned?
4. What are the commercial terms and approval process for the integration route you recommend?