Add custom location url from environment variable

Remove trailing dollar in long and lat placeholder

TEMPLATE.env

@@ -82,4 +82,13 @@ BLOCK_ALL_IPS=False
 # that IP collection is also disabled, and external keys (primary
 # keys) aren't supplied. It will also prevent sessions from spanning
 # one day to another.
-AGGRESSIVE_HASH_SALTING=True
+AGGRESSIVE_HASH_SALTING=True
+
+# Custom location url to link to in frontend.
+# $LATITUDE will get replaced by the latitude, $LONGITUDE will get
+# replaced by the longitude.
+# Examples:
+#  - https://www.openstreetmap.org/?mlat=$LATITUDE&mlon=$LONGITUDE (default)
+#  - https://www.google.com/maps/search/?api=1&query=$LATITUDE,$LONGITUDE
+#  - https://www.mapquest.com/near-$LATITUDE,$LONGITUDE
+LOCATION_URL=https://www.openstreetmap.org/?mlat=$LATITUDE&mlon=$LONGITUDE