Make URL a Field instead a property (#63)

This PR adds a new Field to all existing Models.
As its a data migrations the Migration is added.

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#63

epdb/views.py

@@ -439,16 +439,7 @@ def scenarios(request):
         if request.GET.get('all'):
             return JsonResponse({
                 "objects": [
-                    {"name": s.name, "url": s.full_url, "reviewed": True}
-                    for s in reviewed_scenario_qs.annotate(
-                        full_url=Concat(
-                            Value(s.SERVER_URL + '/package/'),
-                            F("package__uuid"),
-                            Value("/scenario/"),
-                            F("uuid"),
-                            output_field=CharField(),
-                        )
-                    )
+                    {"name": s.name, "url": s.url, "reviewed": True} for s in reviewed_scenario_qs
                 ]
             })