feat(asset-index): add AssetMetadata

[clearloop]

After thinking about it over again, I don't think refactoring AssetId to enum is a better idea, the following is what AssetId is in my current understanding

• AssetId is unique for PINT assets
  • But one asset can have different AssetIds since Assets could be submitted by different accounts.
  • So if we use enum, the enum have to wrap something which can make Assets different from others, and the easiest and the most practical type is number
• The assets PINT served are dynamic
  • Once an asset has been removed, the match AssetId should not be used anymore
  • Whatever any types we set for Assetid, it's hard to avoid using number

---

• Acala/primitives/Currency
• polkadot/xcm/xcm-executor

Changes

• AssetId: + AtLeast32BitUnsigned

Tests

CI

Issues

Closes #102
Closes #115

[mattsse]

AssetId is unique for PINT assets

• But one asset can have different AssetIds since Assets could be submitted by different accounts.

This is one not clear for me, Assets can be submitted by different accounts, but are always unique.

The assets PINT served are dynamic

• Once an asset has been removed, the match AssetId should not be used anymore
• Whatever any types we set for Assetid, it's hard to avoid using number

This is a very good point.

Yes unique int ids make the most sense, I guess the assets pallet does the same, did you have a look?

What we certainly need is some kind of additional metadata struct for every asset, something like

struct AssetInfo<Id> {
    name : Vec<u8>,
    symbol: Vec<u8>,
    id: Id
}

similar to chainlink feed info

I don't think we have a proper storage map for this, we have the MultiAssetRegistry trait that is implemented for the asset_index, that should be extended

[mattsse]

I think keeping Metadata separate will be more convenient

[mattsse]

LGTM