Document till money-safety model, nonce retry design, and verified customer_id assumption

Adds critical_payment_log to the admin_notification_reason enum (fresh installs + ALTER TYPE for existing deploys); corrects the README's false cash-with-change claim; updates Gap Backlog T14 with the scan job stopgap; documents the till flow's clawback/cash-reconciliation model in the Technical Manual; records the frontend's re-tokenize-on-failure design in P11; and marks the P14 customer_id assumption VERIFIED (Square runtime enforces it per its SDK maintainer; only the OpenAPI schema stays ambiguous, so the P12 sandbox test remains the definitive live check).
2026-08-22 00:34:49 +01:00
parent 965da86b64
commit 5fea301e92
6 changed files with 26 additions and 9 deletions
@@ -6,7 +6,7 @@ Nail salon booking platform — Go 1.26.5 backend + SvelteKit 5 SPA + PostgreSQL

 **Booking**: Self-service (customer), walk-in (admin), call-in (admin). Slot reservations prevent double-booking (4 TTL types). **Self-blocking prevention**: `excludeUserID` parameter filters a user's own `RESERVATION` entries from time blocker overlap checks, allowing re-reservation and booking at overlapping slots. **Explicit cancellation**: `DELETE /api/bookings/reserve` releases a user reservation; `DELETE /api/admin/bookings/reserve` releases an admin walk-in/call-in reservation. **Background cleanup**: Centralised cron scheduler (`backend/internal/jobs/`) runs 24 maintenance jobs: reservation/deposit cleanup every 5min, hourly campaign transitions, daily unpaid-booking notifications, staged default hours auto-apply, GDPR anonymization, financial aggregation, and token/code cleanup. Guest accounts with GDPR-compliant anonymization (including `RESERVATION:edit_request:%` scrubbing). Service eligibility based on age + patch test validity. Overlap checks use `FOR UPDATE` row locks inside transactions. Closing-hours validation (`closing_time.go`) resolves both current and staged default hours.

-**Payments**: Square Terminal (in-person, via `CreateTerminalCheckout`) + online card payments via saved cards or new cards tokenized through the Square Web Payments SDK (`cnon:` nonces — new-card entry falls back to `CardEntryUnavailable` only when neither mock mode nor Square credentials are configured). The backend accepts only tokens, never raw PANs (PCI-DSS parity, mirrored in the dev mock). Cash with change calculation. Gift cards (12-digit code or account balance). Saved cards for faster checkout. Tips on completed bookings. Refunds with notice-period tiers and deposit protection (72h/24h thresholds). All payment types: deposit, full, partial, balance, tip. Payment >20% of total promotes `pending_release` bookings back to `confirmed`. Deposit paid is computed from payments on-the-fly. The first 50% of each payment is always carved out as deposit (via `buildSplitRecords`); any overflow beyond the booking total becomes a tip. A bounded PostgreSQL advisory try-lock (`pg_try_advisory_lock`, ~30 × 100ms ≈ 3s bound) serializes payment attempts per-booking to prevent two-tab double-payment races. Gift card purchases insert a pending payment record with VAT before calling Square — the DB transaction commits first, so Square failures leave a retryable pending record (same-key retries reuse it). Three background sweeps close Square's ~24h idempotency-key retention window: `sweep-pending-square-refunds` reconciles/retries stuck refunds (with a 23h age guard), `sweep-stale-pending-payments` fails stale pending payments/till-sales so a late retry cannot issue a second charge, and `sweep-stale-terminal-checkouts` cancels card-machine checkouts still pending at Square after an hour so a never-polled checkout cannot complete into an invisible, untracked charge.
+**Payments**: Square Terminal (in-person, via `CreateTerminalCheckout`) + online card payments via saved cards or new cards tokenized through the Square Web Payments SDK (`cnon:` nonces — new-card entry falls back to `CardEntryUnavailable` only when neither mock mode nor Square credentials are configured). The backend accepts only tokens, never raw PANs (PCI-DSS parity, mirrored in the dev mock). Cash till sales record the gift-card value and are marked completed, with no tendered/change fields. Any change or overpayment is handled manually by the admin at the counter. Gift cards (12-digit code or account balance). Saved cards for faster checkout. Tips on completed bookings. Refunds with notice-period tiers and deposit protection (72h/24h thresholds). All payment types: deposit, full, partial, balance, tip. Payment >20% of total promotes `pending_release` bookings back to `confirmed`. Deposit paid is computed from payments on-the-fly. The first 50% of each payment is always carved out as deposit (via `buildSplitRecords`); any overflow beyond the booking total becomes a tip. A bounded PostgreSQL advisory try-lock (`pg_try_advisory_lock`, ~30 × 100ms ≈ 3s bound) serializes payment attempts per-booking to prevent two-tab double-payment races. Gift card purchases insert a pending payment record with VAT before calling Square — the DB transaction commits first, so Square failures leave a retryable pending record (same-key retries reuse it). Three background sweeps close Square's ~24h idempotency-key retention window: `sweep-pending-square-refunds` reconciles/retries stuck refunds (with a 23h age guard), `sweep-stale-pending-payments` fails stale pending payments/till-sales so a late retry cannot issue a second charge, and `sweep-stale-terminal-checkouts` cancels card-machine checkouts still pending at Square after an hour so a never-polled checkout cannot complete into an invisible, untracked charge.

 **Gift Cards**: Multi-method purchase (cash, card machine, online card, giveaway). Inventory cards for stock management. 24-month rolling expiry. Idle account cleanup (2yr/5yr thresholds). Expired balance recovery with admin audit trail. Transaction audit log. Idempotency keys for purchases.