"""Procurement domain — full P2P platform layer.

Owns the *fact-record + master-data + relational* layer of the Procure-
to-Pay loop:

* **procurement_categories** — first-class category master data
  (software / hardware / cloud / service). Each row carries default
  owner + cost-centre + reminder rules so new POs auto-populate.
* **procurement_suppliers** — replaces the bare ``asset_suppliers``
  phone-book with full vendor master data (tax id, banking, multi-
  contact JSON, payment terms, status).
* **procurement_contracts** + ``_attachments`` + ``_versions`` —
  contracts are first-class entities. Files live on S3
  (``helix-prod-uploads-ap-southeast-1``); version history tracks
  amount / expiry / status changes.
* **procurement_orders** + ``_items`` — purchase orders, with line
  items pointing at the asset / software they fulfill, the four-role
  owner model (business / IT / finance / procurement), and external
  ID hooks for Helian (汇联易) approval + Oracle NetSuite payment.
* **procurement_payments** — outbound payment records (separate from
  the internal ``software_monthly_bills`` per-seat chargeback).
* **software_procurement_meta** — 1:1 sidecar on ``asset_software_
  catalog`` separating *procurement basis* (contract / supplier /
  renewal date) from *operational state* (seat / SSO / offboarding).

The domain does NOT own approval or actual payment execution — those
remain in 汇联易 + Oracle NetSuite. Helix records intent + observed
state + budget reservation + reminders, and exposes a one-click hand-
off (PR 2 wire-up) to push to the finance system.
"""