`UnionOf` types for merged `fungible` and `fungibles` implementations (#2033)
Introduces `UnionOf` types, crafted to merge `fungible` and `fungibles` implementations or two `fungibles` implementations into a single type implementing `fungibles`. This also addresses an issue where `ItemOf` initiates a double drop for an imbalance type, leading to inaccurate total issuance accounting. Find the application of these types in this PR - [link](https://github.com/paritytech/polkadot-sdk/pull/2031), places in code - [1](https://github.com/paritytech/polkadot-sdk/blob/4ec7496f/cumulus/parachains/runtimes/assets/asset-hub-kusama/src/lib.rs#L327), [2](https://github.com/paritytech/polkadot-sdk/blob/4ec7496f /cumulus/parachains/runtimes/assets/asset-hub-kusama/src/lib.rs#L343). --------- Co-authored-by: Liam Aharon <[email protected]> Co-authored-by: joe petrowski <[email protected]> Co-authored-by: Oliver Tale-Yazdi <[email protected]> Co-authored-by: joepetrowski <[email protected]>