feat: add creation timestamp to twin transfer requests for future exp…

…iry handling

docs/architecture/0024-twin-ownership-transfer.md

@@ -40,13 +40,23 @@ Introduce a simple two-step transfer protocol implemented in `pallet-tfgrid` tha
 
 ### Storage
 
-- `TwinTransferRequests: RequestId -> TwinTransferRequest` (twin_id, old_account, new_account)
+- `TwinTransferRequests: RequestId -> TwinTransferRequest` (twin_id, old_account, new_account, created_at)
 - `PendingTransferByTwin: TwinId -> RequestId` (enforces one pending request per Twin)
 - `TwinTransferRequestID: u64` (monotonic counter)
 
 ### Types
 
-- None specific to lifecycle state; a request exists while pending and is removed on accept/cancel.
+- `TwinTransferRequest` includes `created_at: BlockNumber` to record when the request was created.
+  - There is no expiry logic in v1.
+  - Future cleaners (on_finalize/offchain) can use `created_at` to remove stale items if desired.
+
+### Errors and Semantics
+
+- Request flow is capped at one request per twin. If a request already exists, `request_twin_transfer` returns a single error:
+  - `TwinTransferPendingExists` ("cancel the existing request first")
+- Accept flow has no expiry checks; presence of a matching request and correct signer are sufficient.
+- Cancel flow always succeeds for the old owner:
+  - Removes the request and emits `TwinTransferCanceled`.
 
 ## Security Considerations
 
@@ -68,4 +78,4 @@ Introduce a simple two-step transfer protocol implemented in `pallet-tfgrid` tha
 ## References
 
 - Implementation: `substrate-node/pallets/pallet-tfgrid/src/twin_transfer.rs`
-- Extrinsics wiring: `substrate-node/pallets/pallet-tfgrid/src/lib.rs` (call_index 40, 41)
+- Extrinsics wiring: `substrate-node/pallets/pallet-tfgrid/src/lib.rs` (call_index 40, 41, 42)

substrate-node/pallets/pallet-tfgrid/src/lib.rs

@@ -266,13 +266,14 @@ pub mod pallet {
         ValueQuery,
     >;
 
-    // Twin ownership transfer storage types (no status/expiry; pending exists while entry exists)
+    // Twin ownership transfer storage types with creation timestamp 
     #[derive(Encode, Decode, Clone, PartialEq, Eq, TypeInfo, MaxEncodedLen)]
     #[scale_info(skip_type_params(T))]
     pub struct TwinTransferRequest<T: Config> {
         pub twin_id: u32,
         pub old_account: T::AccountId,
         pub new_account: T::AccountId,
+        pub created_at: BlockNumberFor<T>,
     }
 
     #[pallet::storage]

substrate-node/pallets/pallet-tfgrid/src/tests.rs

@@ -15,7 +15,6 @@ const GIGABYTE: u64 = 1024 * 1024 * 1024;
 use crate::pallet::{
     PendingTransferByTwin, TwinIdByAccountID, TwinTransferRequestID, TwinTransferRequests, Twins,
 };
-use pallet_balances::Pallet as BalancesPallet;
 use frame_support::traits::ReservableCurrency;
 
 #[test]

substrate-node/pallets/pallet-tfgrid/src/twin_transfer.rs

@@ -44,10 +44,12 @@ impl<T: Config> Pallet<T> {
         req_id = req_id.saturating_add(1);
         TwinTransferRequestID::<T>::put(req_id);
 
+        let now = <frame_system::Pallet<T>>::block_number();
         let request = TwinTransferRequest::<T> {
             twin_id,
             old_account: old_account.clone(),
             new_account: new_account.clone(),
+            created_at: now,
         };
 
         TwinTransferRequests::<T>::insert(req_id, &request);