change the way of burning util token

Author: thurendous

src/VotingPowerExchange.sol

@@ -133,6 +133,9 @@ contract VotingPowerExchange is AccessControl, EIP712 {
             burningTokenAmount = calculateIncrementedBurningAmount(incrementedVotingPower, currentVotingPower);
         }
 
+        // msg.sender send utilityToken to the sender
+        // exchange role address need to approve this contract to transfer the utilityToken
+        utilityToken.transferFrom(msg.sender, sender, burningTokenAmount);
         // burn utilityToken from the `sender`
         utilityToken.burnByBurner(sender, burningTokenAmount);
 

test/fuzz/FuzzVotingPowerExchange.t.sol

@@ -64,6 +64,7 @@ contract VotingPwoerExchangeTest is Test {
         utilityToken.mint(user, 1_000 * 1e18);
         utilityToken.mint(participant, 100_000 * 1e18);
         utilityToken.mint(participant2, 10_000 * 1e18);
+        utilityToken.mint(exchanger, 10_000 * 1e18);
         vm.stopPrank();
 
         // set the voting power cap to 99e18