Show holidays in visited countries on trip page

Closes: #112

web_view.py

@@ -253,6 +253,19 @@ def trip_page(start: str) -> str:
         if "geojson_filename" in route:
             route["geojson"] = agenda.trip.read_geojson(route.pop("geojson_filename"))
 
+    if trip.end:
+        countries = {c.alpha_2 for c in trip.countries}
+        holidays = [
+            hol
+            for hol in agenda.holidays.get_all(
+                trip.start, trip.end, app.config["DATA_DIR"]
+            )
+            if hol.country.upper() in countries
+        ]
+        holidays.sort(key=lambda item: (item.date, item.country))
+    else:
+        holidays = []
+
     return flask.render_template(
         "trip_page.html",
         trip=trip,
@@ -263,6 +276,7 @@ def trip_page(start: str) -> str:
         routes=routes,
         get_country=agenda.get_country,
         format_list_with_ampersand=format_list_with_ampersand,
+        holidays=holidays,
     )