feat: migrate app routes and business modules

utils/non-idempotent-write-guard.js

@@ -0,0 +1,18 @@
+import { isWriteOutcomeUnknown } from '@/utils/request-outcome.js'
+
+export const createNonIdempotentWriteGuard = () => {
+  let uncertainPayloadSnapshot = ''
+
+  return {
+    begin(payload) {
+      const payloadSnapshot = JSON.stringify(payload)
+      return payloadSnapshot === uncertainPayloadSnapshot ? null : payloadSnapshot
+    },
+
+    recordFailure(payloadSnapshot, error) {
+      if (!isWriteOutcomeUnknown(error)) return false
+      uncertainPayloadSnapshot = payloadSnapshot
+      return true
+    }
+  }
+}