fix: dos if payment id frontran

src/contracts/Grateful.sol

@@ -64,9 +64,6 @@ contract Grateful is IGrateful, Ownable2Step, ReentrancyGuard {
   /// @inheritdoc IGrateful
   mapping(address => CustomFee) public override customFees;
 
-  /// @inheritdoc IGrateful
-  mapping(uint256 => bool) public paymentIds;
-
   /// @inheritdoc IGrateful
   uint256 public performanceFee;
 
@@ -458,12 +455,6 @@ contract Grateful is IGrateful, Ownable2Step, ReentrancyGuard {
       revert Grateful_InvalidAddress();
     }
 
-    // Check payment id
-    if (paymentIds[_paymentId]) {
-      revert Grateful_PaymentIdAlreadyUsed();
-    }
-    paymentIds[_paymentId] = true;
-
     // Apply the fee
     uint256 amountWithFee = applyFee(_merchant, _amount);
     uint256 feeAmount = _amount - amountWithFee;

src/interfaces/IGrateful.sol

@@ -144,6 +144,9 @@ interface IGrateful {
   /// @notice Thrown when the provided address is invalid.
   error Grateful_InvalidAddress();
 
+  /// @notice Thrown when the precomputed address does not match the one-time address created.
+  error Grateful_PrecomputedAddressMismatch();
+
   /*///////////////////////////////////////////////////////////////
                                    VARIABLES
     //////////////////////////////////////////////////////////////*/
@@ -208,13 +211,6 @@ interface IGrateful {
     address _merchant
   ) external view returns (bool isSet, uint256 fee);
 
-  /// @notice Returns if a paymentId has been used.
-  /// @param paymentId The payment id.
-  /// @return isUsed True if the payment id has been used.
-  function paymentIds(
-    uint256 paymentId
-  ) external view returns (bool isUsed);
-
   /*///////////////////////////////////////////////////////////////
                                     LOGIC
     //////////////////////////////////////////////////////////////*/