Generate bahn.expert details link based on trip_id for DBRIS (#36)

Generate bahn.expert details link based on trip_id for DBRIS

This patch adds a conditional for the train details page to
generate the bahn.expert details outlink based on the trip_id
when using DBRIS bahn.de.

This is a lot more reliable compared to concating category and
train number / date. As bahn.expert recently added support for
resolving these HAFAS trip ids to RIS::Journey journeys, the
data quality is also on par.

See https://chaos.social/@marudor/114404980599765615



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Co-authored-by: Birte Kristina Friesel <birte.friesel@uos.de>