feat: add balancer v2 executor

foundry/lib/balancer-labs/v2-interfaces/README.md

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+# <img src="../../logo.svg" alt="Balancer" height="128px">
+
+# Balancer V2 Interfaces
+
+[![NPM Package](https://img.shields.io/npm/v/@balancer-labs/v2-interfaces.svg)](https://www.npmjs.org/package/@balancer-labs/v2-interfaces)
+
+This package contains interfaces used in dependent packages, which makes building systems that interact with Balancer contracts simpler, as the implementation information is not included.
+
+## Overview
+
+### Installation
+
+```console
+$ npm install @balancer-labs/v2-interfaces
+```
+
+### Usage
+
+This package can be used in multiple ways, including interacting with already deployed Pools, or performing local testing. It contains all interfaces used in the system, from the foundational [Vault](contracts/vault/IVault.sol) to very specific contracts (e.g., [Optimism Gas Limit Provider](contracts/liquidity-mining/IOptimismGasLimitProvider.sol)).
+
+The following are a couple code samples to help get you started. To get the address of deployed contracts in both production and test networks, see [`v2-deployments`](../deployments).
+
+Sample contract that joins a Balancer Pool:
+
+````solidity
+pragma solidity ^0.7.0;
+
+// Import Vault interface, error messages, and library for decoding join/exit data.
+import "@balancer-labs/v2-interfaces/contracts/solidity-utils/helpers/BalancerErrors.sol";
+import "@balancer-labs/v2-interfaces/contracts/solidity-utils/openzeppelin/IERC20.sol";
+import "@balancer-labs/v2-interfaces/contracts/pool-weighted/WeightedPoolUserData.sol";
+import "@balancer-labs/v2-interfaces/contracts/vault/IVault.sol";
+import "@balancer-labs/v2-interfaces/contracts/vault/IAsset.sol";
+
+// Import ERC20Helpers for `_asIAsset`
+import "@balancer-labs/v2-solidity-utils/contracts/helpers/ERC20Helpers.sol";
+
+contract JoinBalancerPool {
+    IVault private constant vault = "0xBA12222222228d8Ba445958a75a0704d566BF2C8";
+
+    function joinBalancerPool(bytes32 poolId, address sender, address recipient, uint256[] memory amountsIn, uint256 minBptAmountOut) external {
+        (IERC20[] memory tokens, , ) = vault.getPoolTokens(poolId);
+
+        // Use BalancerErrors to validate input
+        _require(amountsIn.length == tokens.length, Errors.INPUT_LENGTH_MISMATCH);
+
+        // Encode the userData for a multi-token join
+        bytes memory userData = abi.encode(WeightedPoolUserData.JoinKind.EXACT_TOKENS_IN_FOR_BPT_OUT, amountsIn, minBptAmountOut);
+
+        IVault.JoinPoolRequest memory request = IVault.JoinPoolRequest({
+            assets: _asIAsset(tokens),
+            maxAmountsIn: amountsIn,
+            userData: userData,
+            fromInternalBalance: false
+        });
+
+        // Call the Vault to join the pool
+        vault.joinPool(poolId, sender, recipient, request);
+    }
+
+    ...
+}
+```
+
+Sample contract that performs Internal Balance deposits:
+
+```solidity
+pragma solidity ^0.7.0;
+
+import "@balancer-labs/v2-interfaces/contracts/vault/IVault.sol";
+
+contract SimpleDepositor {
+    IVault private constant vault = "0xBA12222222228d8Ba445958a75a0704d566BF2C8";
+
+    function depositFunds(
+        IERC20[] memory tokens,
+        uint256[] memory amounts,
+    ) external {
+      IVault.UserBalanceOp[] memory ops = new IVault.UserBalanceOp[](tokens.length);
+
+      for (uint256 i = 0; i < tokens.length; ++i) {
+        ops[i] = IVault.UserBalanceOp({
+          kind: IVault.UserBalanceOpKind.DEPOSIT_INTERNAL,
+          asset: IAsset(tokens[i]),
+          amount: amounts[i],
+          sender: address(this),
+          recipient: address(this)
+        });
+      }
+
+      vault.manageUserBalance(ops);
+    }
+}
+````
+
+Sample contract that performs Flash Loans:
+
+```solidity
+pragma solidity ^0.7.0;
+
+import "@balancer-labs/v2-interfaces/contracts/vault/IVault.sol";
+import "@balancer-labs/v2-interfaces/contracts/vault/IFlashLoanRecipient.sol";
+
+contract FlashLoanRecipient is IFlashLoanRecipient {
+    IVault private constant vault = "0xBA12222222228d8Ba445958a75a0704d566BF2C8";
+
+    function makeFlashLoan(
+        IERC20[] memory tokens,
+        uint256[] memory amounts,
+        bytes memory userData
+    ) external {
+      vault.flashLoan(this, tokens, amounts, userData);
+    }
+
+    function receiveFlashLoan(
+        IERC20[] memory tokens,
+        uint256[] memory amounts,
+        uint256[] memory feeAmounts,
+        bytes memory userData
+    ) external override {
+        require(msg.sender == vault);
+        ...
+    }
+}
+```
+
+### Notes
+
+In addition to interfaces, it also includes a small number of libraries that encapsulate enum types for particular pools (e.g., [StablePoolUserData](contracts/pool-stable/StablePoolUserData.sol), and functions for working with encoding and decoding `userData`. (See the `balancer-js` package for TypeScript versions of these utilities.)
+
+One of the most commonly included libraries is [BalancerErrors](contracts/solidity-utils/helpers/BalancerErrors.sol). To save bytecode, Balancer V2 does not use the standard `require(<condition>, 'error string')`. Instead, BalancerErrors defines `_require` and `_revert` functions. These take a numerical constant instead of a string, and return a fixed-length code, which can be converted to plain text using TypeScript utilities.
+
+## Licensing
+
+[GNU General Public License Version 3 (GPL v3)](../../LICENSE).
+
+```
+
+```