fix: Don't show non-applicable directional alerts on the line diagram

[joshlarson]

Scope

Asana Ticket: ❗[AM Alerts] 🐞 Directional alerts are shown on both directions of the line diagram

Implementation

• Add another utility function called matchesDirection for alerts, and use it to filter alerts before they're passed into the <LineDiagram /> component.
  • This had to happen in <ScheduleDirection /> or downstream of there, because when you switch directions on the line diagram page, the direction ID change is captured in state, but not in the direction ID passed in to the component (which is what's available upstream of <ScheduleDirection />). If we did the filtering anywhere upstream of <ScheduleDirection /> (e.g. in <SchedulePage />), then the alerts that are visible on the line diagram would be based on which direction you were looking at when you first navigated to the page, not what direction you're looking at now.

Screenshots

Note the same line diagram in the other direction:

How to test

Create a station bypass or suspension that only affects a single direction, and visit the line diagram page for the affected route and switch directions.

[thecristen]

Yea, solid!