Review the AI's percentage-refunds PR

Author: AI coding assistant · Base: main · Component: Refunds API

Goal

An AI assistant opened this pull request. Review it the way you would at work: leave comments on the lines that have problems (what is wrong and what to change), then approve or request changes.

The PR adds POST /v1/refunds/percent, so support agents and merchants can refund "25% of this payment" without working out the amount. It moves real money, so read it as you would a change to the ledger. The author's PR description is in the Review tab, next to the diff.

Context

• The service is Paylane, a small payments API (FastAPI + SQLModel + SQLite). README.md explains how to run it and docs/CONTRACT.md is the contract every endpoint follows (money, refunds, idempotency, errors).
• Your workspace is checked out on the PR branch, so you can read the code, run the tests and call the API in the preview. The AI assistant is available if you want it.

What a good review looks like

• Comments sit on the exact lines they are about and say what is wrong, why it matters and what to change.
• Don't take the PR description's word for it; check each claim against the code and the contract.
• Finish with a decision: Approve or Request changes, plus a short summary.