Multi-backend support

Squashed commit of the following:

commit 92518024ba295456358618c0e8180bd8e996fdf1
Author: Birte Kristina Friesel <birte.friesel@uos.de>
Date:   Fri Jul 26 18:39:46 2024 +0200

    add_or_update station: remove superfluos 'new backend id := old backend id'

commit df21c20c6e4c86454f8a9ac69121404415217f2a
Author: Birte Kristina Friesel <birte.friesel@uos.de>
Date:   Fri Jul 26 18:35:51 2024 +0200

    revert connection targets min_count to 3

commit be335cef07d0b42874f5fc1de4a1d13396e8e807
Author: Birte Kristina Friesel <birte.friesel@uos.de>
Date:   Fri Jul 26 18:20:05 2024 +0200

    mention backend selection in API documentation

commit 9f41828fb4f18fd707e0087def3032e8d4c8d7d8
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Thu Jul 25 20:19:23 2024 +0200

    use_history: not all backends provide route data in departure monitor

commit 09714b4d89684b8331d0e96f564a4c7432318f70
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Thu Jul 25 20:11:44 2024 +0200

    disambiguation: pass correct hafas parameter

commit 8cdf1120fc32155dc6525be64601b7c10a9c7f52
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Thu Jul 25 20:11:28 2024 +0200

    _checked_in: hide Zuglauf link for non-db checkins

commit 7455653f541198e0e0a6d11aed421487ffdb6285
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Thu Jul 25 20:01:47 2024 +0200

    debug output

commit b9cda07f85601a58ea32dbdacdd5399f302db52b
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Thu Jul 25 19:09:07 2024 +0200

    fix remaining get_connection_targets / get_connecting_trains_p invocations

commit 2759d7258c37c7498905cfe19f6b4c4f6d16bd21
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Wed Jul 24 20:50:12 2024 +0200

    support non-DB HAFAS backends (WiP)

0 files changed, 0 insertions, 0 deletions