feat: Pass along more enhanced JSON fields from RTR

[losvedir]

This adds two new fields to the TripUpdates_enhanced.json file, which RTR produces but currently Concentrate ignores. The fields are used by realtime signs. With the recent OL surge, there was a question about updating realtime-signs to use concentrate's output, in order to have access to CR data. They decided against it, for now, but it seemed like a good idea to me to update concentrate so that it would be possible in the future, if a situation like this came up again. The two fields are in StopTimeUpdate and are:

• stops_away - this is a field that says how many stations away the predicted train is from the stop the prediction is for.
• passthrough_time - this is arrival_time || departure_time for SKIPPED stops, prior to those values being nullified by RTR. realtime-signs uses this to play the "next train does not take passengers, please stand back from the yellow line" message.

I think both of them could arguably be implemented differently in realtime-signs such that these values aren't necessary but that's a larger lift, and in an app that our team doesn't maintain anymore. I didn't want to put that work on @PaulJKim , but I am open to potentially implementing it over there myself. It didn't seem so bad to me to have extra fields in our enhanced JSON here, so I went with the easier solution, but I could be convinced to take the other approach.

[github-actions]

Coverage of commit 7690be8

Summary coverage rate:
  lines......: 94.9% (1034 of 1090 lines)
  functions..: 78.0% (347 of 445 functions)
  branches...: no data found

Files changed coverage rate:
                                                            |Lines       |Functions  |Branches    
  Filename                                                  |Rate     Num|Rate    Num|Rate     Num
  ================================================================================================
  lib/concentrate/encoder/trip_updates_enhanced.ex          | 100%      4| 100%     3|    -      0
  lib/concentrate/parser/gtfs_realtime_enhanced.ex          |96.3%     54|87.5%    16|    -      0
  lib/concentrate/stop_time_update.ex                       |91.3%     23|64.7%    34|    -      0

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[paulswartz]

• stops_away: is it possible to calculate this inside the app, using the vehicle_id from the TripUpdate?
• passthough_time: I wonder if this should be implemented differently now, with keeping the times in the feed along with SKIPPED?

In general, I'm wary of adding data to Concentrate or the API that only has one client. Do you see other use cases for this data?

[paulswartz]

Code itself looks fine, but I think we need some more discussion about the general concept of adding these fields.

[PaulJKim]

@losvedir let me know if you want to discuss how to implement those features without those fields. I can sort of see how we could go about that, but if you want to lay out what you have in mind I'm more than happy to take on the work.

[bklebe]

We've determined this is no longer necessary.