Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/contracts/mocks/ERC1271WalletMock.sol

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../access/Ownable.sol";
+import "../interfaces/IERC1271.sol";
+import "../utils/cryptography/ECDSA.sol";
+
+contract ERC1271WalletMock is Ownable, IERC1271 {
+    constructor(address originalOwner) {
+        transferOwnership(originalOwner);
+    }
+
+    function isValidSignature(bytes32 hash, bytes memory signature) public view override returns (bytes4 magicValue) {
+        return ECDSA.recover(hash, signature) == owner() ? this.isValidSignature.selector : bytes4(0);
+    }
+}
+
+contract ERC1271MaliciousMock is IERC1271 {
+    function isValidSignature(bytes32, bytes memory) public pure override returns (bytes4) {
+        assembly {
+            mstore(0, 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff)
+            return(0, 32)
+        }
+    }
+}