Keep cancelled trips & skipped stop times from GTFS-RT Trip Updates

[Copilot]

GTFS-RT trip updates can mark a trip as CANCELLED or a stop time as SKIPPED. Previously these were always removed from schedule data. This adds opt-in support to retain them as cancelled timestamps for UI layers that can handle them.

Changes

• Schedule.Timestamp — adds cancelled: Boolean? field with full JSON serialization, equals/hashCode/toString support (mirrors existing realTime/oldSchedule pattern)
• Schedule.ScheduleStatusFilter — adds includeCancelledTimestamps: Boolean? flag (default false) with JSON round-trip support
• GTFSRealTimeTripUpdatesProviderExt — threads includeCancelledTimestamps through processRDTripUpdates → processRDTripUpdate → applyDelaySTU:
  • CANCELED trip + flag=true → keep all trip timestamps, set cancelled=true
  • DELETED trip → always removed (agency intent to hide; unaffected by flag)
  • SKIPPED stop time + flag=true → keep timestamp, set cancelled=true
  • All above with flag=false → existing removal behavior unchanged
• GTFSRealTimeTripUpdatesProvider — passes filter.isIncludeCancelledTimestampsOrDefault() into the processing pipeline

// Enable in filter to retain cancelled/skipped timestamps
val filter = Schedule.ScheduleStatusFilter(rds).apply {
    setIncludeCancelledTimestamps(true)
}

// Downstream: check before rendering
if (timestamp.isCancelled) { /* show strikethrough / cancelled badge */ }

UI integration tracked in mtransitapps/mtransit-for-android#163.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Status > keep cancelled trips & skipped stop time from GTFS-RT Trip Updates</issue_title>
<issue_description>GTFS Real Time trip update can make a trip cancelled or a stop time skipped, these are currently removed from the data since the main app UI cannot yet handle cancelled Schedule.Timestamp.

• update ScheduleStatusFilter to add "include cancelled timestamp" boolean (default false)
• update Schedule.Timestamp to add cancelled boolean (default false)
• in GTFSRealTimeTripUpdatesProviderExt. if the new filter boolean is true, keep the schedule timestamp instead of removing it and update it's "cancelled" boolean value to true.
• do check for tripUpdate.trip.scheduleRelationship as CANCELLED (ignore DELETED since it means transit agency wants to hide trip( as well as stopTimeUpdate.scheduleRelationship` as SKIPPED
• add unit test to cover for these new use cases (filter boolean and cancelled boolean(

UI change will be made in: mtransitapps/mtransit-for-android#163

Links:

• https://gtfs.org/documentation/realtime/feed-entities/trip-updates/
• https://gtfs.org/documentation/realtime/reference/#message-stoptimeupdate</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Status > keep cancelled trips & skipped stop time from GTFS-RT Trip Updates #98

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