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/admin.py

@@ -7,8 +7,8 @@ class InterventionAdmin(admin.ModelAdmin):
     list_display = [
         "id",
         "title",
-        "created_on",
-        "deleted_on",
+        "created",
+        "deleted",
     ]