Dummy contract to access a struct member

StructMemberGetter.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity >=0.8.15;

contract StructMemberGetter {
    error NotAuthorized(address caller);

    struct MyStruct {
        address owner;
    }

    mapping(uint256 => MyStruct) internal myStructs;

    modifier onlyOwner(uint256 id) {
        if (myStructs[id].owner != msg.sender) {
            revert NotAuthorized(msg.sender);
        }
        _;
    }

    constructor(uint256 id) {
        myStructs[id] = MyStruct({ owner: msg.sender });
    }

    function getOwner(uint256 id) public view returns (address theOwner) {
        theOwner = myStructs[id].owner;
    }

    function getBlockTimestamp(uint256 id) onlyOwner(id) external view returns (uint256 timestamp) {
        timestamp = block.timestamp;
    }
}