Advanced Commerce API one-time charges: SKU per purchase vs a stable SKU catalog?

Hi,

For one-time charges with server-set prices that vary per purchase, item.SKU in OneTimeChargeCreateRequest can be either:

1. A stable SKU per item type, e.g. com.example.itemtype, reused across purchases.
2. A unique SKU per purchase, e.g. com.example.itemtype.<uuid>, so each Sales Report row maps to one transaction.

The SKU docs only state a 128-character limit and that App Store Connect does not store it. I have a few questions regarding the SKU management:

1. Should we expect SKU rules to change, such as enforced uniqueness, character restrictions, or immutability?
2. Any recommended SKU format beyond the length limit?