Modelling transfer information

[McToel]

I'm using FPTF for some time in https://bahnvorhersage.de/. However, I really struggle to include transfer information in the format. For Bahn-Vorhersage I need to include reliability indicators for transfers, but also other information like how much time is planned for the transfer, which is often available without having any information about the walking distance. Also, I try to mark whether a transfer is on the same platform or not. While some of the features can be modelled using a walking leg it does not always make sense. For example, having a planned transfer duration but no walking distance and also a walking leg should not have a transfer reliability.

I suggest adding something like a transfer leg that can have such information and that could replace walking legs. These could be optional. Maybe this is not ideal and there are better suggestions.

I currently have some spare time and could contribute to this format after nothing really happened in the last 6 years as far as I can tell. If this project is "dead" or the suggestion seems completely unreasonable, I might just implement it for my project, and it will not end up in here.

This might also be an opportunity to release other changes that are long planned for a v2.