This can result in users paying higher fees than intended and having their CDPs reflect a higher debt than the actual eBTC received. 
The problem is present in both the _openCdpForCallback and _adjustCdpCallback functions. Looking at the _openCdpForCallback function: 
https://github.com/code-423n4/2024-06-badger/blob/9173558ee1ac8a78a7ae0a39b97b50ff0dd9e0f8/ebtc-zap-router/src/LeverageZapRouterBase.sol#L276-L292
CDP is opened for the full flData.eBTCToMint amount, but then a fee is deducted from this amount and sent to the zapFeeReceiver. This means:
For example, if a user wants to mint 100 eBTC and the zapFeeBPS is 50 (0.5%):
This could be costly in scenarios where the user is close to the liquidation threshold. They might believe they have more buffer than they actually do, potentially leading to unexpected liquidations as the case may be.
Recalculate the eBTC amount to mint or adjust before performing the CDP operation, subtracting the fee amount first. Then, open or adjust the CDP with this reduced amount, ensuring the CDPs debt accurately reflects the eBTC the user receives. Finally, transfer the calculated fee to the zapFeeReceiver.
