#86·Register AIR and AUSD in the Asset Registry

This proposal will add AIR and AUSD to the Asset Registry.

Proposal hash: 0x7df8ae3e0b2f3b8d3053a3cb617c1f6b6e7db01eea7a672ae737619662f2714a

AUSD is already registered but using the CurrencyId::AUSD currency identifier and we want to now register it as CurrencyId::ForeignAsset so that we can drop AUSD as a hardcoded asset in our currencyId type, essentially. So that pre image registers the AUSD asset as a foreign assets and sets all the currency CurrencyId::AUSD asset metadata to blank values. This entry will be removed from storage once we drop that Id variant.

Forum post: https://gov.centrifuge.io/t/council-motion-86-register-air-and-ausd-in-the-asset-registry/5336