Include train line data in rail API

[houbly]

The API endpoints currently being accessed for rail searches on this app are:

api.wmnetwork.co.uk
/rail/v2/station?q=
/rail/v2/station/:id
/rail/v1/departuresandarrivals/:id

What

• Currently, the departures and arrivals API doesn't include the train line which each station runs on which means we can't add functionality to accurately filter train stations that run on the same line. (See design at https://www.figma.com/file/0EvvTWMZXlKDrQ9WcINGsn/Station-and-Stops?node-id=577%3A13300)
• This might be fixed by doing one of the following:
  • Including the train lines each station runs on (e.g. Cross city, Walsall) in the /rail/v1/departuresandarrivals/:id endpoint so they can be cross-referenced between stations to determine whether two stations are on the same line
  • Creating a new endpoint where you can query the name of station line to find out which stations run on them
  • Creating a new endpoint where you can query a station to find out the departure routes that will be taken from the station