Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/contracts/mocks/crosschain/bridges.sol

@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../../utils/Address.sol";
+import "../../vendor/polygon/IFxMessageProcessor.sol";
+
+abstract contract BaseRelayMock {
+    // needed to parse custom errors
+    error NotCrossChainCall();
+    error InvalidCrossChainSender(address sender, address expected);
+
+    address internal _currentSender;
+
+    function relayAs(address target, bytes calldata data, address sender) external virtual {
+        address previousSender = _currentSender;
+
+        _currentSender = sender;
+
+        (bool success, bytes memory returndata) = target.call(data);
+        Address.verifyCallResultFromTarget(target, success, returndata, "low-level call reverted");
+
+        _currentSender = previousSender;
+    }
+}
+
+/**
+ * AMB
+ */
+contract BridgeAMBMock is BaseRelayMock {
+    function messageSender() public view returns (address) {
+        return _currentSender;
+    }
+}
+
+/**
+ * Arbitrum
+ */
+contract BridgeArbitrumL1Mock is BaseRelayMock {
+    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable state-variable-assignment
+    address public immutable inbox = address(new BridgeArbitrumL1Inbox());
+    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable state-variable-assignment
+    address public immutable outbox = address(new BridgeArbitrumL1Outbox());
+
+    function activeOutbox() public view returns (address) {
+        return outbox;
+    }
+
+    function currentSender() public view returns (address) {
+        return _currentSender;
+    }
+}
+
+contract BridgeArbitrumL1Inbox {
+    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable state-variable-assignment
+    address public immutable bridge = msg.sender;
+}
+
+contract BridgeArbitrumL1Outbox {
+    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable state-variable-assignment
+    address public immutable bridge = msg.sender;
+
+    function l2ToL1Sender() public view returns (address) {
+        return BridgeArbitrumL1Mock(bridge).currentSender();
+    }
+}
+
+contract BridgeArbitrumL2Mock is BaseRelayMock {
+    function wasMyCallersAddressAliased() public view returns (bool) {
+        return _currentSender != address(0);
+    }
+
+    function myCallersAddressWithoutAliasing() public view returns (address) {
+        return _currentSender;
+    }
+}
+
+/**
+ * Optimism
+ */
+contract BridgeOptimismMock is BaseRelayMock {
+    function xDomainMessageSender() public view returns (address) {
+        return _currentSender;
+    }
+}
+
+/**
+ * Polygon
+ */
+contract BridgePolygonChildMock is BaseRelayMock {
+    function relayAs(address target, bytes calldata data, address sender) external override {
+        IFxMessageProcessor(target).processMessageFromRoot(0, sender, data);
+    }
+}

backend/lib/openzeppelin-contracts/contracts/mocks/crosschain/receivers.sol

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.4;
+
+import "../../access/Ownable.sol";
+import "../../crosschain/amb/CrossChainEnabledAMB.sol";
+import "../../crosschain/arbitrum/CrossChainEnabledArbitrumL1.sol";
+import "../../crosschain/arbitrum/CrossChainEnabledArbitrumL2.sol";
+import "../../crosschain/optimism/CrossChainEnabledOptimism.sol";
+import "../../crosschain/polygon/CrossChainEnabledPolygonChild.sol";
+
+abstract contract Receiver is CrossChainEnabled {
+    // we don't use Ownable because it messes up testing for the upgradeable contracts
+    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable state-variable-assignment
+    address public immutable owner = msg.sender;
+
+    function crossChainRestricted() external onlyCrossChain {}
+
+    function crossChainOwnerRestricted() external onlyCrossChainSender(owner) {}
+}
+
+/**
+ * AMB
+ */
+contract CrossChainEnabledAMBMock is Receiver, CrossChainEnabledAMB {
+    /// @custom:oz-upgrades-unsafe-allow constructor
+    constructor(address bridge) CrossChainEnabledAMB(bridge) {}
+}
+
+/**
+ * Arbitrum
+ */
+contract CrossChainEnabledArbitrumL1Mock is Receiver, CrossChainEnabledArbitrumL1 {
+    /// @custom:oz-upgrades-unsafe-allow constructor
+    constructor(address bridge) CrossChainEnabledArbitrumL1(bridge) {}
+}
+
+contract CrossChainEnabledArbitrumL2Mock is Receiver, CrossChainEnabledArbitrumL2 {}
+
+/**
+ * Optimism
+ */
+contract CrossChainEnabledOptimismMock is Receiver, CrossChainEnabledOptimism {
+    /// @custom:oz-upgrades-unsafe-allow constructor
+    constructor(address bridge) CrossChainEnabledOptimism(bridge) {}
+}
+
+/**
+ * Polygon
+ */
+contract CrossChainEnabledPolygonChildMock is Receiver, CrossChainEnabledPolygonChild {
+    /// @custom:oz-upgrades-unsafe-allow constructor
+    constructor(address bridge) CrossChainEnabledPolygonChild(bridge) {}
+}