Support white-listing of locations

[stechu]

One common error in XCM is when sending to unsupported location. It would be great for xtoken to provide an optional support for white-listing locations.

[xlc]

We could have a location filter, and another pallet to manage the whitelist registration

[stechu]

We could have a location filter, and another pallet to manage the whitelist registration

yeah, adding interface for hooking the other pallet that manage the whitelist registration and then xtoken can return an UnsupportedLocation error rather than returning XCMExecutionFailed would be nice.

[Dengjianping]

Yeah, some teams are using hardcoded locations, some are using a on-chain manager to manage locations.

If xtoken is going to support getting location by manager, we can add an associated type to Config, just like:

#[pallet::config]
pub trait Config: frame_system::Config {
    // ...
    type WhiteListingMultiLocations: WhiteListingMultiLocations<Self::CurrencyId, Self::Balance>;
    // ...
}

And this trait WhiteListingMultiLocations should include methods like get supported location by CurrencyId.

pub trait WhiteListingMultiLocations<CurrencyId, Balance> {
    fn get_supported_locations(&self, currency_id: CurrencyId) -> Option<MultiLocation>;
    fn get_all_supported_locations(&self) -> Option<Vec<MultiLocation>>;
    fn get_xcm_fee(&self, currency_id: CurrencyId) -> Balance;
    // fn get_asset(&self, currency_id: CurrencyId) -> AssetInfo;
    // or more methods 
}

[xlc]

PRs are welcome.

[xlc]

closed by #714