[0.9.40] Add `query_account_balances` runtime api for pallet assets.

[hbulgarini]

During release 0.9.40, the query_account_balances runtime api for querying the assets balances were implemented.

We can have the details here:
paritytech/substrate#13352

This is what it has to be added in the runtime (please check the assets_common):

	impl assets_common::runtime_api::FungiblesApi<
		Block,
		AccountId,
	> for Runtime
	{
		fn query_account_balances(account: AccountId) -> Result<xcm::VersionedMultiAssets, assets_common::runtime_api::FungiblesAccessError> {
			use assets_common::fungible_conversion::{convert, convert_balance};
			Ok([
				// collect pallet_balance
				{
					let balance = Balances::free_balance(account.clone());
					if balance > 0 {
						vec![convert_balance::<KsmLocation, Balance>(balance)?]
					} else {
						vec![]
					}
				},
				// collect pallet_assets (TrustBackedAssets)
				convert::<_, _, _, _, TrustBackedAssetsConvertedConcreteId>(
					Assets::account_balances(account.clone())
						.iter()
						.filter(|(_, balance)| balance > &0)
				)?,
				// collect pallet_assets (ForeignAssets)
				convert::<_, _, _, _, ForeignAssetsConvertedConcreteId>(
					ForeignAssets::account_balances(account)
						.iter()
						.filter(|(_, balance)| balance > &0)
				)?,
				// collect ... e.g. other tokens
			].concat().into())
		}
	}

CC: @stiiifff @valentinfernandez1

[hbulgarini]

In addition to this i have noticed that the assets-common, contains a more interesting MultiAssetConverter/convert_ref implemention that the one we have in our xcm-primitives.

I see a couple of improvements in the asset-common as:

• Better error management.
• It returns the amount in addition to the asset id.

This should also be considered in the asset-registry pallet that we are implementing.

Taking into account that modifying the asset-registry is a different topic that adding this runtime api, i think that this enhancement should be applied in a different issue after this task is done. Thinking out loud, i see a period of time where both XCM primitives will cohexist until the xcm-primitives is removed or replaced.

[valentinfernandez1]

I like this implementation. We would have to remove this part since we don't have ForeignAssets.

....
// collect pallet_assets (ForeignAssets)
convert::<_, _, _, _, ForeignAssetsConvertedConcreteId>(
    ForeignAssets::account_balances(account)
        .iter()
        .filter(|(_, balance)| balance > &0)
)?,

But everything else looks good to me. I can add it today.

In regards to your second comment, why do you consider that both convert_ref should coexist in the same file??

[hbulgarini]

In regards to your second comment, why do you consider that both convert_ref should coexist in the same file??

Basically because i'm not 100% sure which changes are needed over the asset registry by using the new convert_ref function. In case we need to change something (if it's technically feasible), i would apply these new impls from assets_common and implement the runtime api and once that is ready in a different PR i would modify the old impls by the new ones. However i saw that in your draft PR #202 you have to modify the FungiblesAdapter, so probably everything should be changed in one PR.

[stiiifff]

@valentinfernandez1 Closing this as I believe this was done, right ? Re-open if not.