Improve GTFS-RT Support

[felixguendling]

No description provided.

[derhuerst]

I'm curious: Specifically, how does this PR improve MOTIS' GTFS-RT support?

[felixguendling]

Thank you for your interest.

We implemented the MOTIS GTFS-RT code with focus on the Switzerland GTFS from SBB. When trying the GTFS-RT stream from Poznan (mentioned in #181), I noticed that we do not cover some parts of the GTFS-RT specification (specifically how trips and stops can be identified). So these changes should support the Poznan GTFS-RT data - and therefore all GTFS-RT feeds that work similarly.

The GTFS-RT functionality in MOTIS is rather new and may be a little bit rough around the edges. We are trying hard to improve support - at least for all features that are used in practice.

After that works, I'm also planning a major refactoring of the code handling GTFS-RT to improve compactness and maintainability.

[felixguendling]

Seems like delays seem to be working now for this feed!! 🚀 😀

@wkulesza thank you for providing the feed URL!

However, from the GTFS-static documentation about stop_sequence in stops.txt

The values must increase along the trip but do not need to be consecutive.

For the GTFS-RT-feed to work properly, these values have to be consecutive and start with zero. This is the case for most feeds. We're planning to add support for non-zero-based and non-consecutive stop_sequence numbers nonetheless.