interface GPv2Authentication {
    function isSolver(address) external view returns (bool);
}

address public manager;
mapping(address => bool) private solvers;

event ManagerChanged(address newManager);
event SolverAdded(address solver);
event SolverRemoved(address solver);

function initializeManager(address manager_) external initializer;

function setManager(address manager_) external onlyManagerOrOwner;

function addSolver(address solver) external onlyManager;

function removeSolver(address solver) external onlyManager;

function isSolver(address solver) external view returns (bool);