Take modification time into account when merging reservations

That is, a newer one now always takes precedence, even if it comes first
in the input list.

autotests/mergedata/mtime.lhs.json

+[
+    {
+        "@type": "FlightReservation",
+        "airplaneSeat": "06D",
+        "modifiedTime": "2019-12-19T00:00:00",
+        "reservationFor": {
+            "@type": "Flight",
+            "airline": {
+                "@type": "Airline",
+                "iataCode": "XX"
+            },
+            "arrivalAirport": {
+                "@type": "Airport",
+                "iataCode": "CPH",
+                "name": "Copenhagen"
+            },
+            "arrivalTime": "2020-01-05T12:15:00.000",
+            "departureAirport": {
+                "@type": "Airport",
+                "iataCode": "PRG",
+                "name": "Prag"
+            },
+            "departureTime": "2020-01-05T10:55:00.000",
+            "flightNumber": "1234"
+        },
+        "reservationNumber": "XXX007"
+    }
+]

autotests/mergedata/mtime.merged.json

+[{
+    "@context": "http://schema.org",
+    "@type": "FlightReservation",
+    "airplaneSeat": "27E",
+    "modifiedTime": "2020-01-04T00:00:00",
+    "reservationFor": {
+        "@type": "Flight",
+        "airline": {
+            "@type": "Airline",
+            "iataCode": "DX"
+        },
+        "arrivalAirport": {
+            "@type": "Airport",
+            "iataCode": "CPH",
+            "name": "Copenhagen"
+        },
+        "arrivalTime": "2020-01-05T12:15:00",
+        "departureAirport": {
+            "@type": "Airport",
+            "iataCode": "PRG",
+            "name": "Prag"
+        },
+        "departureDay": "2021-01-05",
+        "departureTime": "2020-01-05T10:55:00",
+        "flightNumber": "1234"
+    },
+    "reservationNumber": "XXX007",
+    "reservedTicket": {
+        "@type": "Ticket",
+        "ticketToken": "aztecCode:M1..."
+    }
+}]

autotests/mergedata/mtime.rhs.json

+[
+    {
+        "@context": "http://schema.org",
+        "@type": "FlightReservation",
+        "airplaneSeat": "27E",
+        "modifiedTime": "2020-01-04T00:00:00",
+        "reservationFor": {
+            "@type": "Flight",
+            "airline": {
+                "@type": "Airline",
+                "iataCode": "DX"
+            },
+            "arrivalAirport": {
+                "@type": "Airport",
+                "iataCode": "CPH"
+            },
+            "departureAirport": {
+                "@type": "Airport",
+                "iataCode": "PRG"
+            },
+            "departureDay": "2021-01-05",
+            "flightNumber": "1234"
+        },
+        "reservationNumber": "XXX007",
+        "reservedTicket": {
+            "@type": "Ticket",
+            "ticketToken": "aztecCode:M1..."
+        }
+    }
+]
+

src/mergeutil.cpp

@@ -534,6 +534,15 @@ QVariant MergeUtil::merge(const QVariant &lhs, const QVariant &rhs)
         return {};
     }
 
+    // prefer the element with the newer mtime, if we have that information
+    if (JsonLd::canConvert<Reservation>(lhs) && JsonLd::canConvert<Reservation>(rhs)) {
+        const auto lhsDt = JsonLd::convert<Reservation>(lhs).modifiedTime();
+        const auto rhsDt = JsonLd::convert<Reservation>(rhs).modifiedTime();
+        if (lhsDt.isValid() && rhsDt.isValid() && rhsDt < lhsDt) {
+            return MergeUtil::merge(rhs, lhs);
+        }
+    }
+
     auto res = lhs;
     const auto mo = QMetaType(res.userType()).metaObject();
     for (int i = 0; i < mo->propertyCount(); ++i) {