Created|Deleted refactoring

* refactors base attributes created and deleted into UserActionLogEntry foreign keys
* refactors all related queries and process logic
* fixes binding_on into binding_date in intervention/detail/view.html
* adds basic __str__ for some models
*

intervention/views.py

@@ -28,10 +28,10 @@ def index_view(request: HttpRequest):
 
     # Filtering by user access is performed in table filter inside of InterventionTableFilter class
     interventions = Intervention.objects.filter(
-        deleted_on=None,  # not deleted
+        deleted=None,  # not deleted
         next_version=None,  # only newest versions
     ).order_by(
-        "-created_on"
+        "-created__timestamp"
     )
     table = InterventionTable(
         request=request,
@@ -128,8 +128,7 @@ def open_view(request: HttpRequest, id: str):
     # Fetch data, filter out deleted related data
     intervention = get_object_or_404(Intervention, id=id)
     compensations = intervention.compensations.filter(
-        deleted_on=None,
-        deleted_by=None,
+        deleted=None,
     )
     has_access = intervention.has_access(user=request.user)