feat(token): add governance token and mintable test token

src/FluxToken.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.36;
+
+import {Erc20} from "./Erc20.sol";
+
+/// @title Governance and staking reward token, minted by the active gauge.
+contract FluxToken is Erc20 {
+    address public minter;
+
+    event MinterChanged(address indexed oldMinter, address indexed newMinter);
+
+    constructor(address minterAddress) Erc20("Flux", "FLUX") {
+        minter = minterAddress;
+        emit MinterChanged(address(0), minterAddress);
+    }
+
+    modifier onlyMinter() {
+        require(msg.sender == minter, "FluxToken: FORBIDDEN");
+        _;
+    }
+
+    function setMinter(address newMinter) external onlyMinter {
+        emit MinterChanged(minter, newMinter);
+        minter = newMinter;
+    }
+
+    function mint(address to, uint256 value) external onlyMinter {
+        _mint(to, value);
+    }
+
+    function burn(uint256 value) external {
+        _burn(msg.sender, value);
+    }
+}

src/TestErc20.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.36;
+
+import {Erc20} from "./Erc20.sol";
+
+/// @title Freely mintable ERC20 for tests and liquidity bootstrapping.
+contract TestErc20 is Erc20 {
+    constructor(string memory tokenName, string memory tokenSymbol, uint256 initialSupply)
+        Erc20(tokenName, tokenSymbol)
+    {
+        _mint(msg.sender, initialSupply);
+    }
+
+    function mint(address to, uint256 value) external {
+        _mint(to, value);
+    }
+}