Contract

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.4;

contract SimpleUserProxy {
    error Unauthorized();

    address public owner;
    bool public initialized;

    function initialize(address _owner) external {
        if (initialized) revert Unauthorized();

        owner = _owner;
        initialized = true;
    }

    function doCall(address _target, bytes calldata _data) external payable {
        if (msg.sender != owner) revert Unauthorized();

        (bool success, bytes memory result) = _target.call{value: msg.value}(
            _data
        );
        if (!success) {
            assembly {
                revert(add(result, 32), mload(result))
            }
        }
    }
}

{
  "optimizer": {
    "enabled": true,
    "runs": 800
  },
  "outputSelection": {
    "*": {
      "*": [
        "evm.bytecode",
        "evm.deployedBytecode",
        "devdoc",
        "userdoc",
        "metadata",
        "abi"
      ]
    }
  },
  "libraries": {}
}

[{"inputs":[],"name":"Unauthorized","type":"error"},{"inputs":[{"internalType":"address","name":"_target","type":"address"},{"internalType":"bytes","name":"_data","type":"bytes"}],"name":"doCall","outputs":[],"stateMutability":"payable","type":"function"},{"inputs":[{"internalType":"address","name":"_owner","type":"address"}],"name":"initialize","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"initialized","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"owner","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"}]