public HttpResponse AddUserToTrip(string tripId)
        {
            if (!User.IsAuthenticated)
            {
                //return Redirect("/Users/Login");

                return(Error($"401 Unauthorized")); // This way is more ser-friendly
            }

            var userId = User.Id;

            if (tripsService.IsUserInTrip(userId, tripId))
            {
                return(Redirect($"/Trips/Details?tripId={tripId}"));
            }

            if (tripsService.HasAvaibleSeats(tripId))
            {
                return(Error("No seats avaible."));
            }

            tripsService.AddUserToTrip(userId, tripId);

            return(Redirect("/Trips/All"));
        }
        public HttpResponse AddUserToTrip(string tripId)
        {
            if (!IsUserSignIn())
            {
                return(Redirect("/Users/Login"));
            }

            var userId = GetUserId();

            if (tripsService.IsUserInTrip(userId, tripId))
            {
                return(Redirect($"/Trips/Details?tripId={tripId}"));
            }

            if (tripsService.HasAvaibleSeats(tripId))
            {
                return(Error("No seats avaible."));
            }

            tripsService.AddUserToTrip(userId, tripId);

            return(Redirect("/Trips/All"));
        }