Show ticket number for train tickets when available

This differs from the booking reference in some case, and is e.g.
needed to sign in to the Renfe onboard WiFi.

src/app/TrainPage.qml

@@ -293,7 +293,7 @@ App.DetailsPage {
             Kirigami.Separator {
                 Kirigami.FormData.label: i18n("Booking")
                 Kirigami.FormData.isSection: true
-                visible: referenceLabel.visible || underNameLabel.visible
+                visible: referenceLabel.visible || underNameLabel.visible || ticketNumberLabel.visible
             }
             QQC2.Label {
                 id: referenceLabel
@@ -301,6 +301,12 @@ App.DetailsPage {
                 text: reservation.reservationNumber
                 visible: reservation.reservationNumber
             }
+            QQC2.Label {
+                id: ticketNumberLabel
+                Kirigami.FormData.label: i18n("Ticket number:")
+                text: root.currentReservation.reservedTicket.ticketNumber
+                visible: ticketNumberLabel.text !== "" && ticketNumberLabel.text != referenceLabel.text
+            }
             QQC2.Label {
                 id: underNameLabel
                 Kirigami.FormData.label: i18n("Under name:")