Improve cross-border train information

[MoritzWeber0]

Cross-border trains are complex, especially when it comes to the booking of FIP 50 tickets. It's hard to find out whether international journeys can be booked via specific booking platforms and the country pages usually don't list the booking information. Some especially hard cases are trains that cross more than two countries, for example the Railjet from Berlin to Budapest via Czechia and Slovakia.

We should consider adding a separate page, like the night train page, for those complex connections with their corresponding booking platforms.

Another improvement idea could be to indicate on booking platforms if they support the booking of cross-border FIP 50 tickets to neighbouring countries.