Function map_model::make::walking_turns::make_walking_turns

pub fn make_walking_turns(map: &Map, i: &Intersection) -> Vec<Turn>

Looks at all sidewalks (or lack thereof) in counter-clockwise order around an intersection. Based on adjacency, create a SharedSidewalkCorner or a Crosswalk. UnmarkedCrossings are not generated here; another process later “downgrades” crosswalks to unmarked.