private async Task <IHttpActionResult> GenerateTokenResponse(SystemUser user, TimeSpan ticketLifetime)
{
var identity = await _systemUserManager.GenerateUserIdentityAsync(user, OAuthDefaults.AuthenticationType);
var properties = ApplicationOAuthProvider.CreateProperties(user.UserName);
var ticket = new AuthenticationTicket(identity, properties);
ticket.Properties.ExpiresUtc = DateTime.UtcNow.Add(ticketLifetime);
var token = AuthConfig.OAuthOptions.AccessTokenFormat.Protect(ticket);
return(Json(new { token }, DefaultSerializerSettings.Instance));
}