fix: Idempotent cart completion (#9231)

What
- Store result of cart-completion workflow for three days by default
  - This enables the built-in idempotency mechanism to kick-in, provided the same transaction ID is used on workflow executions
- Return order from cart-completion workflow if the cart has already been completed
  - In case transaction ID is not used on workflow executions, we still only want to complete a cart once

packages/core/orchestration/src/transaction/transaction-orchestrator.ts

@@ -1148,7 +1148,7 @@ export class TransactionOrchestrator extends EventEmitter {
           queue.push({ obj: obj[key], level: [...level] })
         } else if (key === "action") {
           if (actionNames.has(obj.action)) {
-            throw new Error(`Action "${obj.action}" is already defined.`)
+            throw new Error(`Step ${obj.action} is already defined in workflow.`)
           }
 
           actionNames.add(obj.action)