/// <summary>
/// Add roles to user's list of roles.
/// </summary>
/// <param name="policy">admin configuration parameters, pass in null for defaults</param>
/// <param name="user">user name</param>
/// <param name="roles">role names. Predefined roles are listed in Role.cs</param>
public void GrantRoles(AdminPolicy policy, string user, IList<string> roles)
{
AdminCommand command = new AdminCommand();
command.GrantRoles(cluster, policy, user, roles);
}