Easy finding of ‘rest stops’ /service stations (UK) along current route

> I've been on long journeys where I need to find a stop using Google/Apple Maps via CarPlay, but it only shows places closest to drive to, often requiring a detour off the motorway.
>
> My request is for a menu/list showing available stops along my current route, so I know how long until I can stop for a pee, rather than driving around in the middle of nowhere about to burst (or stop for rest/food, but needing a pee has been my main need so far😂).

Source: https://discord.com/channels/1313185644134006886/1318130203259572224

No files, tests, or entry points are named. Start by reviewing how the current route and CarPlay navigation are represented, then clarify the source of UK service-station data and the expected stop list. Done means a user can see suitable stops along the current route without needing to search for nearby places or take an unnecessary detour.

Written by the indexing model from the issue text.