[weather] Add optional "Observation Timestamp" to dataengine data

dataengines/weather/ions/bbcukmet/ion_bbcukmet.cpp

@@ -903,6 +903,9 @@ void UKMETIon::updateWeather(const QString& source)
 
     data.insert(QStringLiteral("Place"), weatherData.stationName);
     data.insert(QStringLiteral("Station"), weatherData.stationName);
+    if (weatherData.observationDateTime.isValid()) {
+        data.insert(QStringLiteral("Observation Timestamp"), weatherData.observationDateTime);
+    }
     if (!weatherData.obsTime.isEmpty()) {
         data.insert(QStringLiteral("Observation Period"), weatherData.obsTime);
     }

dataengines/weather/ions/envcan/ion_envcan.cpp

@@ -1436,7 +1436,12 @@ void EnvCanadaIon::updateWeather(const QString& source)
     }
 
     // Real weather - Current conditions
+    if (weatherData.observationDateTime.isValid()) {
+        data.insert(QStringLiteral("Observation Timestamp"), weatherData.observationDateTime);
+    }
+
     data.insert(QStringLiteral("Observation Period"), weatherData.obsTimestamp);
+
     if (!weatherData.condition.isEmpty()) {
         data.insert(QStringLiteral("Current Conditions"), i18nc("weather condition", weatherData.condition.toUtf8().data()));
     }

dataengines/weather/ions/ion.h

@@ -44,7 +44,8 @@
 * "Longitude": float, longitude of the weather station in decimal degrees, optional
 *
 * Data about last observation:
-* "Observation Period": string, free text string for time of observation, optional, TODO: get standardized datetime
+* "Observation Period": string, free text string for time of observation, optional
+* "Observation Timestamp": datetime (with timezone), time of observation, optional
 * "Current Conditions": string, free text string for current weather observation, optional
 * "Condition Icon": string, xdg icon name for current weather observation, optional
 * "Temperature": float, using general temperature unit, optional

dataengines/weather/ions/noaa/ion_noaa.cpp

@@ -564,7 +564,12 @@ void NOAAIon::updateWeather(const QString& source)
     }
 
     // Real weather - Current conditions
+    if (weatherData.observationDateTime.isValid()) {
+        data.insert(QStringLiteral("Observation Timestamp"), weatherData.observationDateTime);
+    }
+
     data.insert(QStringLiteral("Observation Period"), weatherData.observationTime);
+
     const QString conditionI18n = weatherData.weather == QLatin1String("N/A") ? i18n("N/A") : i18nc("weather condition", weatherData.weather.toUtf8().data());
 
     data.insert(QStringLiteral("Current Conditions"), conditionI18n);