To withdraw user's original token on original chain, FE(front-end) needs to do the following things:
1.
Get basic pegged configs through cBridge gateway. The same api as general token transfer
2.
Check user's on-chain token allowance for cBridge PeggedTokenBridge contract. If the allowance is not enough for burn, trigger the corresponding on-chain approve flow
3.
Submit on-chain burn request to cBridge PeggedTokenBridge contract on pegged chain
4.
Get transfer status repeatedly to check whether the burn/withdraw is complete.