Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/contracts/mocks/ERC20Reentrant.sol

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "../token/ERC20/ERC20.sol";
+import "../token/ERC20/extensions/ERC4626.sol";
+
+contract ERC20Reentrant is ERC20("TEST", "TST") {
+    enum Type {
+        No,
+        Before,
+        After
+    }
+
+    Type private _reenterType;
+    address private _reenterTarget;
+    bytes private _reenterData;
+
+    function scheduleReenter(Type when, address target, bytes calldata data) external {
+        _reenterType = when;
+        _reenterTarget = target;
+        _reenterData = data;
+    }
+
+    function functionCall(address target, bytes memory data) public returns (bytes memory) {
+        return Address.functionCall(target, data);
+    }
+
+    function _beforeTokenTransfer(address from, address to, uint256 amount) internal override {
+        if (_reenterType == Type.Before) {
+            _reenterType = Type.No;
+            functionCall(_reenterTarget, _reenterData);
+        }
+        super._beforeTokenTransfer(from, to, amount);
+    }
+
+    function _afterTokenTransfer(address from, address to, uint256 amount) internal override {
+        super._afterTokenTransfer(from, to, amount);
+        if (_reenterType == Type.After) {
+            _reenterType = Type.No;
+            functionCall(_reenterTarget, _reenterData);
+        }
+    }
+}