[Vault Module]: Refactor vault contract to only manage vault state #51
Description
Description
Currently, the vault contract stores users' funds and interacts directly with the token contracts. We want to make sure that the vault is not making any external calls.
- Vault should only be responsible for managing vault state(balances, collateralization ratio)
- Introduce Vault IDs when creating vaults
- Abstract out Liquidation function from Vault module