make facebook urls for events editable

dnscms/events/models.py

@@ -192,6 +192,11 @@ class EventPage(Page):
         FieldPanel("body"),
         FieldPanel("categories", widget=forms.CheckboxSelectMultiple),
         FieldPanel("organizers", widget=forms.SelectMultiple),
+        FieldPanel(
+            "facebook_url",
+            heading="Facebook-lenke",
+            help_text="Lenke direkte til arrangementet på Facebook.",
+        ),
         MultiFieldPanel(
             heading="Priser og billettkjøp",
             children=ticket_panels,