commerce: provider-neutral payment-request envelope (8 tests) — Phase 5 ext

payment.sx — payment-request materialises {:order :amount :currency :return-url}
at the IO edge (amount from the ledger, currency/return-url host-supplied), so
lib/commerce stays vendor-agnostic; SumUp/Stripe adapters live in the orders
service and order-settle!(ref, amount) is the resume seam. pending-payments
enumerates suspended orders + envelopes (host poller seam). Gotcha handled: a
Scheme string flow-payload round-trips back wrapped as {:scm-string ...} —
unwrapped via scm->string. Total 209/209 across 13 suites.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/commerce/payment.sx

@@ -0,0 +1,41 @@
+;; lib/commerce/payment.sx — provider-neutral payment-request envelope.
+;;
+;; The order flow (order.sx) suspends on `(request 'payment oid)` — it carries
+;; ONLY the order-id and calls no provider. This layer materialises, at the IO
+;; edge, the envelope a provider adapter needs to initiate payment:
+;;
+;;   {:order oid :amount <ledger total> :currency C :return-url U}
+;;
+;; amount comes from the ledger (the :created quote total); currency + return-url
+;; are host/provider config (legitimately host-supplied). The engine stays
+;; vendor-agnostic: SumUp/Stripe/etc. adapters consume this envelope, and
+;; order-settle!(ref, amount) is the vendor-neutral resume seam. No provider
+;; SDK, HTTP, or webhook parsing lives here — that is the orders service's job.
+
+(define payment-request (fn (b oid currency return-url) {:order oid :amount (order-total b oid) :return-url return-url :currency currency}))
+
+(define payment-request-order (fn (pr) (get pr :order)))
+(define payment-request-amount (fn (pr) (get pr :amount)))
+(define payment-request-currency (fn (pr) (get pr :currency)))
+(define payment-request-return-url (fn (pr) (get pr :return-url)))
+
+;; A Scheme string carried as a flow payload round-trips back to SX wrapped as
+;; {:scm-string "..."}; unwrap it to the bare order-id.
+(define
+  scm->string
+  (fn
+    (v)
+    (if (and (dict? v) (has-key? v :scm-string)) (get v :scm-string) v)))
+
+;; Host poller seam: every order currently suspended awaiting payment, each with
+;; its envelope. A provider adapter iterates these, initiates payment, and later
+;; calls order-settle! when the webhook arrives. Needs the flow env.
+(define
+  pending-payments
+  (fn
+    (env b currency return-url)
+    (let
+      ((reqs (flow-run-in env "(flow-host-requests)")))
+      (map
+        (fn (r) {:id (first r) :request (payment-request b (scm->string (nth r 2)) currency return-url)})
+        (filter (fn (r) (= (nth r 1) "payment")) reqs)))))