Owned.sol

// SPDX-License-Identifier: GPL-3.0
// Docgen-SOLC: 0.8.15

pragma solidity ^0.8.15;

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
  address public owner;
  address public nominatedOwner;

  constructor(address _owner) {
    require(_owner != address(0), "Owner address cannot be 0");
    owner = _owner;
    emit OwnerChanged(address(0), _owner);
  }

  function nominateNewOwner(address _owner) external virtual onlyOwner {
    nominatedOwner = _owner;
    emit OwnerNominated(_owner);
  }

  function acceptOwnership() external virtual {
    require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
    emit OwnerChanged(owner, nominatedOwner);
    owner = nominatedOwner;
    nominatedOwner = address(0);
  }

  modifier onlyOwner() {
    _onlyOwner();
    _;
  }

  function _onlyOwner() private view {
    require(msg.sender == owner, "Only the contract owner may perform this action");
  }

  event OwnerNominated(address newOwner);
  event OwnerChanged(address oldOwner, address newOwner);
}