refactor: consolidate IERC20 in src/interfaces, drop openzeppelin-contracts submodule

.gitmodules

@@ -4,6 +4,3 @@
 [submodule "lib/solady"]
 	path = lib/solady
 	url = https://github.com/vectorized/solady
-[submodule "lib/openzeppelin-contracts"]
-	path = lib/openzeppelin-contracts
-	url = https://github.com/OpenZeppelin/openzeppelin-contracts

src/across/AcrossV3Helper.sol

@@ -4,7 +4,7 @@ pragma solidity >=0.8.0;
 /// library imports
 import "forge-std/Test.sol";
 import {IAcrossSpokePoolV3} from "./interfaces/IAcrossSpokePoolV3.sol";
-import {IERC20} from "./interfaces/IERC20.sol";
+import {IERC20} from "../interfaces/IERC20.sol";
 
 /// @title AcrossV3 Helper
 /// @notice helps simulate AcrossV3 message relaying

src/debridge/DebridgeDlnHelper.sol

@@ -4,7 +4,7 @@ pragma solidity >=0.8.0;
 /// library imports
 import "forge-std/Test.sol";
 import {IExternalCallExecutor} from "./interfaces/IExternalCallExecutor.sol";
-import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import {IERC20} from "../interfaces/IERC20.sol";
 import {IDlnDestination, Order} from "./interfaces/IDlnDestination.sol";
 
 /// @title Debridge DLN Helper

src/interfaces/IERC20.sol

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v5.1.0) (token/ERC20/IERC20.sol)
+
+pragma solidity >=0.8.0;
+
+/// @dev Interface of the ERC-20 standard. Vendored from OpenZeppelin contracts to keep pigeon self-contained.
+interface IERC20 {
+    event Transfer(address indexed from, address indexed to, uint256 value);
+    event Approval(address indexed owner, address indexed spender, uint256 value);
+
+    function totalSupply() external view returns (uint256);
+
+    function balanceOf(address account) external view returns (uint256);
+
+    function transfer(address to, uint256 value) external returns (bool);
+
+    function allowance(address owner, address spender) external view returns (uint256);
+
+    function approve(address spender, uint256 value) external returns (bool);
+
+    function transferFrom(address from, address to, uint256 value) external returns (bool);
+}

test/Across.t.sol

@@ -8,7 +8,7 @@ import {console2} from "forge-std/console2.sol";
 import {AcrossV3Helper} from "src/across/AcrossV3Helper.sol";
 import {IAcrossSpokePoolV3} from "src/across/interfaces/IAcrossSpokePoolV3.sol";
 import {IAcrossV3Interpreter} from "src/across/interfaces/IAcrossV3Interpreter.sol";
-import {IERC20} from "src/across/interfaces/IERC20.sol";
+import {IERC20} from "src/interfaces/IERC20.sol";
 import {console} from "forge-std/console.sol";
 
 contract Target {

test/Debridge.t.sol

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 pragma solidity >=0.8.0;
 
-import {IERC20} from "src/across/interfaces/IERC20.sol";
+import {IERC20} from "src/interfaces/IERC20.sol";
 import "forge-std/Test.sol";
 
 import {DebridgeHelper} from "src/debridge/DebridgeHelper.sol";

test/DebridgeDln.t.sol

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 pragma solidity >=0.8.0;
 
-import {IERC20} from "lib/openzeppelin-contracts/contracts/token/ERC20/IERC20.sol";
+import {IERC20} from "src/interfaces/IERC20.sol";
 import "forge-std/Test.sol";
 
 import {DebridgeDlnHelper} from "../src/debridge/DebridgeDlnHelper.sol";

test/Stargate.t.sol

@@ -4,6 +4,7 @@ pragma solidity >=0.8.0;
 import "forge-std/Test.sol";
 
 import {LayerZeroHelper} from "src/layerzero/LayerZeroHelper.sol";
+import {IERC20} from "src/interfaces/IERC20.sol";
 
 interface IStargateRouter {
     struct lzTxObj {
@@ -25,14 +26,6 @@ interface IStargateRouter {
     ) external payable;
 }
 
-interface IERC20 {
-    function approve(address spender, uint256 amount) external returns (bool);
-
-    function balanceOf(address account) external view returns (uint256);
-
-    function transfer(address to, uint256 amount) external returns (bool);
-}
-
 contract Target {
     uint256 public value;