Ability to add referral commissions

We would like to implement a referral program that offers monetary incentives for referrals involving webstores and custom orders.

The system should allow webstores to act as referrers. When a webstore generates a sale, the associated referrer should receive a commission. This commission can either be a percentage of the sale or a fixed dollar amount.

Here are the key requirements:

1. Referral Tracking: Implement a mechanism to track which webstore referred each sale.
2. Commission Calculation: Ensure that the commission for each sale can be set as either a percentage or a fixed dollar amount.
3. Commission Statements: Integrate the commission information into the referrer's commission statement, so they can see their earnings from the referrals.

We envision this as a seamless addition to our existing system, allowing us to incentivize referrals effectively and transparently.