public Task AddToRoleAsync(ApplicationUser user, string roleName, CancellationToken cancellationToken)
{
if (user == null)
{
throw new ArgumentNullException("user");
}
if (roleName == "")
{
throw new ArgumentNullException("roleName");
}
var result = _authService.AddToRole(user.Id, roleName);
user.ApplicationRoles.Add(result.Item);
return(Task.FromResult(result.Item));
}