Add planning documents for Forte music store platform

17 domain design docs covering architecture, accounts, inventory,
rentals, lessons, repairs, POS, payments, batch repairs, delivery,
billing, accounting, deployment, licensing, installer, and backend
tech architecture. Plus implementation roadmap (doc 18) and
personnel management (doc 19).

Key design decisions documented:
- company/location model (multi-tenant + multi-location)
- member entity (renamed from student to support multiple adults)
- Stripe vs Global Payments billing ownership differences
- User/location/terminal licensing model
- Valkey 8 instead of Redis

planning/04_Domain_Rentals.md

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+Music Store Management Platform
+
+Domain Design: Rentals
+
+
+
+# 1. Overview
+
+The Rentals domain manages instrument rental contracts, recurring billing, and rent-to-own tracking. Rentals are one of the most financially complex areas of the platform due to recurring Stripe subscriptions, multi-rental billing consolidation, and rent-to-own equity calculations.
+
+
+
+# 2. Rental Types
+
+Type
+
+Description
+
+Month-to-month
+
+Standard rental — continues until returned or cancelled. No purchase obligation.
+
+Rent-to-own
+
+A percentage of each payment applies toward purchase price. Customer can buy out at any time.
+
+Short-term
+
+Hourly, daily, or weekly rental. Flat fee, no subscription. Common for events.
+
+Lease purchase
+
+Fixed-term contract with defined end purchase price.
+
+
+
+# 3. Database Schema
+
+## 3.1 rental
+
+Column
+
+Type
+
+Notes
+
+id
+
+uuid PK
+
+
+
+company_id
+
+uuid FK
+
+
+
+account_id
+
+uuid FK
+
+Billing account
+
+member_id
+
+uuid FK
+
+Member who has the instrument
+
+inventory_unit_id
+
+uuid FK
+
+Specific instrument rented
+
+rental_type
+
+enum
+
+month_to_month | rent_to_own | short_term | lease_purchase
+
+status
+
+enum
+
+active | returned | cancelled | completed
+
+start_date
+
+date
+
+
+
+end_date
+
+date
+
+Null for open-ended rentals
+
+monthly_rate
+
+numeric(10,2)
+
+Monthly charge amount
+
+deposit_amount
+
+numeric(10,2)
+
+Security deposit collected
+
+deposit_returned
+
+boolean
+
+
+
+billing_group
+
+varchar
+
+Groups rentals for consolidated billing
+
+stripe_subscription_id
+
+varchar
+
+Stripe subscription reference
+
+stripe_subscription_item_id
+
+varchar
+
+Line item if consolidated
+
+rto_purchase_price
+
+numeric(10,2)
+
+Rent-to-own: full purchase price
+
+rto_equity_percent
+
+numeric(5,2)
+
+% of payment applied to equity
+
+rto_equity_accumulated
+
+numeric(10,2)
+
+Total equity built toward purchase
+
+notes
+
+text
+
+
+
+legacy_id
+
+varchar
+
+AIM rental contract ID
+
+created_at
+
+timestamptz
+
+
+
+
+
+## 3.2 rental_payment
+
+Records each individual payment made against a rental — populated via Stripe webhook events.
+
+id, rental_id, account_id, stripe_invoice_id, stripe_payment_intent_id,amount, rto_equity_applied, payment_date, status (paid|failed|refunded), created_at
+
+
+
+# 4. Rent-to-Own Logic
+
+When a rental is of type rent_to_own, each payment applies a percentage toward the purchase price.
+
+- rto_equity_accumulated increases by (monthly_rate × rto_equity_percent) each payment
+
+- Buyout amount = rto_purchase_price − rto_equity_accumulated
+
+- Staff can offer buyout at any time — triggers inventory_unit status change to 'sold'
+
+- On buyout, Stripe subscription is cancelled and a one-time charge is created for remaining balance
+
+- Invoice shows accumulated equity and remaining buyout balance
+
+
+
+# 5. Billing Consolidation
+
+## 5.1 Consolidated Billing
+
+When billing_group is set to the same value on multiple rentals for the same account, they share one Stripe subscription with multiple line items. One charge per month covers all grouped rentals.
+
+
+
+## 5.2 Split Billing
+
+When billing_group is null, the rental has its own independent Stripe subscription. Useful when a customer wants rentals charged on different dates.
+
+
+
+## 5.3 Adding a Rental Mid-Cycle
+
+- If consolidating: add new line item to existing subscription — Stripe prorates automatically
+
+- If split: create new standalone subscription with requested billing date
+
+- Invoice shows prorated amount for partial first month
+
+
+
+# 6. Return Workflow
+
+- Staff records return — captures condition assessment
+
+- inventory_unit status updated to 'available' (or 'in_repair' if damage found)
+
+- Stripe subscription cancelled or line item removed
+
+- Deposit refund processed if applicable — logged in audit trail
+
+- Final invoice generated for any partial month charges
+
+- If damage found, repair ticket created automatically and linked to rental record