Add new dispatchables to PalletXcm to allow remote locking

[IkerAlus]

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Motivation

At the moment, chains implementing the PalletXcm do not allow their users to utilise the remote locking functionalities introduced in XCM v3. There are no interfaces exposed directly to users to create XCM messages with the instructions LockAsset, UnlockAsset, etc.

Request

Implement several dispatchables in the PalletXcm to allow the user journey for remote locking as explained in the examples of the XCM docs: https://paritytech.github.io/xcm-docs/journey/locks/locks.html

Solution

Following the original vision of XCM v3: Remote locking the idea would be to implement two new dispatchables as:

• lock_asset(origin, asset: MultiAsset, unlocker: MultiLocation): Locks asset owned by origin with ID (b"xcm_lock", unlocker).encode(). Sends a NoteAssetLocked message to unlocker with asset and origin (converted to a MultiLocation).
• unlock_asset(origin, asset: MultiAsset, locker: MultiLocation): Sends an UnlockAsset instruction to locker for asset IFF there is a registered remote lock for asset and it is currently unused.

[bkchr]

With allowing execute_xcm in pallet-xcm this should be solved? Aka you can just write a XCM message that does what you want to do?

[acatangiu]

With allowing execute_xcm in pallet-xcm this should be solved? Aka you can just write a XCM message that does what you want to do?

Yes, exactly! We should focus on building (off-chain) tools to create these specialized XCMs that can then be dispatched on any XCM-enabled chain.

(I just opened an RFC describing the same idea for asset transfers #4736)