The Index field is a collections.Item that stores the current $USDN rebasing multiplier (math.LegacyDec).
const IndexKey = []byte("index")The Paused field is a collections.Item that stores the current paused state (boolean).
const PausedKey = []byte("paused")The Principal field is a mapping (collections.Map) between user addresses ([]byte) and their principal amount (math.Int) of their $USDN balance.
const PrincipalPrefix = []byte("principal/")