Network: Connect Footway<>Centerline to Generated Sidewalk

[tordans]

Example:

• https://a-b-street.github.io/speedwalk/#17.66/52.763668/13.246949
• https://www.mapillary.com/app/?pKey=1623087731621290&focus=photo&lat=52.7641425&lng=13.2451492&z=17

I just added the crossing=informal to signal that the only way to use this footway is to just cross the road and cross the grass-verge.

I did not add the separate crossing way given that it is only an informal crossing, so the separate sidewalk is not connected.

Do we expect the "generate corssings" step to add the missing link here?
I kind of did but I am not sure…

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Related #70

[dabreegster]

This isn't related to informal, it's just because the topology isn't detected and handled yet. This is a case where the crossing node is directly connected to a footway on one side, and we only need to generate the crossing way on the other side. I'll work on this.

[tordans]

Another case:

https://a-b-street.github.io/speedwalk/#

I added some crossing nodes there but this did not resolve the issue.

[tordans]

Another case:

The inner circle inside the roundabout on the left (image)

https://a-b-street.github.io/speedwalk/#19/52.745085/13.264451

[dabreegster]

I started #74 to resolve this, but I'm still working through some false positives and false negatives where it's adding too much / too little. I'll check these cases too.

[dabreegster]

The logic for creating crossing ways currently tries to make a perpendicular line based on where the yellow crossing node is on the road. Here that _definitely_ fails. What we really want instead is to find the nearest point to the corssing node on a sidewalk on each side of the road. Maybe I've been overthinking how we forcibly generate a perpendicular line. In the common case, that nearest point will be perpendicular anyway. I'll try some things.

[tordans]

This is another nice test case around a roundabout
https://a-b-street.github.io/speedwalk/#18.38/52.733225/13.244858

(Only those two cases, the other I change in OSM afterwards)