static string GetRedirectLocation(
            NancyContext context,
            string authenticationId, 
            IDocumentSession documentSession)
        {
            var member = documentSession.GetMemberByAuth(Constants.TwitterAuth.AuthType, authenticationId);

            if (member == null)
                return Paths.SignUpForm();

            var returnUrl = context.GetReturnUrl();

            return returnUrl ?? Paths.Member(member.Alias);
        }