Enforce immutability of published timetable snapshot#5934

vpaturet merged 2 commits intoopentripplanner:dev-2.xopentripplanner/OpenTripPlanner:dev-2.xfrom

entur:use_immutable_collections_in_timetable_snapshotentur/OpenTripPlanner-LegacyHSLFork:use_immutable_collections_in_timetable_snapshotCopy head branch name to clipboard