Update promotional price for a single item

Updates the promotional price.

Use this API to update or delete an existing promotional price as well as set up a new promotional price.

• To set a new promotional price or update an existing one, set the pricing attribute `processMode` to `UPSERT`.
• To delete a promotional price, set the pricing attribute `processMode` to `DELETE`.
• To delete all promotions for a SKU, set `replaceAll` to an empty payload.

For more information and usage examples, refer to the Marketplace Promotions API Guide.