# payments-api

Kong routing/policy layer for the **payments** slice of
`classic-models-api` (see `/Users/stephanetailland/git/classic-models-api`),
split out per the DDD decomposition in `../kong-konnect-deployment-strategy.md`.
The backend itself stays a single monolith — only Kong does the domain
split. Structure mirrors `../customers-api`, not `../catalog-api` — see
`../STATUS.md` section 18 for why (`catalog-api`'s two-route MCP pattern
has a latent bug; `customers-api`'s single-route pattern is the corrected
one to copy going forward).

Two exposure surfaces, both proxying to the real `classic-models-api`
backend:
- **REST** (`kong/rest/`) — 6 routes over `Payment`, which uses a
  **composite key** (`customernumber` + `checknumber`, not a single id
  like `Customer`/`Product`) — both URI segments are captured and passed
  through to the backend's own composite-key URL pattern.
- **MCP** (`kong/mcp/`) — `list-payments`/`get-payment` (all 5 roles) and
  `create-payment` (admin only — verified against `PaymentPermission`'s
  actual logic in `authentication/permissions.py`, not guessed: writes are
  admin-only in practice, `customer` can only write their own via the
  REST API directly, not exposed as an MCP tool). **One `KongRoute` for
  all three MCP HTTP methods**, one `ai-mcp-proxy` binding — see
  `../STATUS.md` section 18 for why this matters (a second route +
  binding for the same plugin creates a duplicate-tool-name bug, found
  and fixed on `customers-mcp`, built correctly here from the start).

| Route | Method | Backend path |
|---|---|---|
| `/payments/v1/payments/` | GET, POST | `/classic-models/api/v1/payments/` |
| `/payments/v1/payments/{customernumber}/{checknumber}/` | GET, PUT, PATCH, DELETE | `/classic-models/api/v1/payments/{customernumber}/{checknumber}/` |
| `/payments-mcp` | GET, POST, DELETE | MCP streamable-http (tools call into the REST routes above) |

## Auth

`openid-connect` on both surfaces, distinct audience each (`payments-api`
for REST, `mcp-payments` for MCP) with a real RFC 8693 exchange chain:
MCP → `payments-api` → `classic-models-api`, same pattern as
`catalog-api`/`customers-api`. IdP is the local Keycloak
(`https://keycloak.sttlab.local/realms/classic-models`) — see
`../STATUS.md` sections 15/16. `payments-api-audience` and
`mcp-payments-audience` client scopes + `payments-api`/`mcp-payments`
resource clients created on the local Keycloak, attached to
`token-exchange-broker`'s default scopes (REST audience) and to
`librechat`'s optional scopes (MCP audience) respectively — no dedicated
protocol mappers on either new client itself, same practice as every
other domain built this session. `mcp-payments`'s OAuth callback added to
`librechat`'s `redirectUris`, and a `payments-mcp` server entry added to
LibreChat's `librechat.yaml` (`infra-librechat` repo).

## Other policies

Per-consumer rate limiting, response caching (GET/HEAD), audit log
(`http-log`, endpoint still a placeholder — no real log collector in this
lab, same caveat as the other domains).

## Structure

Same `dev/` + `kong/rest/` layout as `customers-api`. Deploy key
(`kong-v2/payments-api/git-deploy-key`) is a **copy of `catalog-api`'s**,
not a freshly generated one — per the user's explicit instruction this
session ("no reason a working key for catalog-api wouldn't work for
customers-api"), the same reused key is used here too rather than minting
yet another one per domain.