This fixes users being logged out whenever following an external link to
travelynx in Safari (iOS/macOS)

iOS Safari does not send session cookies when following links to PWAs using
the apple-mobile-web-app-capable tag. This is not documented on
<https://developer.apple.com/library/archive/documentation/AppleApplications/Reference/SafariWebContent/ConfiguringWebApplications/ConfiguringWebApplications.html>,
though I can't say whether it is a bug in Safari or lacking documentation.

See <https://github.com/foosel/OctoPrint/issues/1792> for a more detailed
description of this type of issue.

At the moment, the heuristic used to determine connection targets is quite
simple: $station is a target iff there were at least two trips in the past
6 weeks with checkin at the current destination station and checkout at
$station.

Todo / enhanhement options:

* Consider current origin station as well, i.e.: $station is a target
  iff there were at least two trips in the past 6 weeks which are preceded by
  a trip from the current origin station and (same as above)
* Make connection links clickable once the current journey has ended.
  Connections need to be added to _checked_out as well for this to work.