membershipworks: Convert EventExt.details_timestamp to GeneratedField

was waiting on Django 5.0.5 to fix
https://code.djangoproject.com/ticket/35350

membershipworks/admin.py

@@ -160,7 +160,7 @@ class EventAdmin(DjangoObjectActions, admin.ModelAdmin):
             else:
                 fields.append(field.name)
         fields.insert(fields.index("end") + 1, "duration")
-        fields.append("_details_timestamp")
+        fields.append("details_timestamp")
         return fields
 
     @admin.display(ordering="title")
@@ -178,10 +178,6 @@ class EventAdmin(DjangoObjectActions, admin.ModelAdmin):
             obj.url,
         )
 
-    @admin.display(description="Last details fetch")
-    def _details_timestamp(self, obj):
-        return naturaltime(obj.details_timestamp)
-
     @takes_instance_or_queryset
     def fetch_details(self, request, queryset):
         scrape_event_details(queryset)

membershipworks/migrations/0018_eventext_details_timestamp.py

@@ -0,0 +1,25 @@
+# Generated by Django 5.0.6 on 2024-05-08 16:44
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("membershipworks", "0017_eventext_registrations_alter_eventinvoice_pdf"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="eventext",
+            name="details_timestamp",
+            field=models.GeneratedField(
+                db_persist=False,
+                expression=models.Func(
+                    models.Func(models.F("details___ts"), function="FROM_UNIXTIME"),
+                    template="CONVERT_TZ(%(expressions)s, @@session.time_zone, 'UTC')",
+                ),
+                output_field=models.DateTimeField(),
+                verbose_name="Last details fetch",
+            ),
+        ),
+    ]

membershipworks/models.py

@@ -520,14 +520,6 @@ class EventExtManager(models.Manager):
                 ExpressionWrapper(F("duration"), models.IntegerField()) * F("count"),
                 models.DurationField(),
             ),
-            # TODO: this could be a GeneratedField, but that
-            # currently breaks saving when the primary key is
-            # provided (Django 5.0.1)
-            details_timestamp=Func(
-                Func(F("details___ts"), function="FROM_UNIXTIME"),
-                template="CONVERT_TZ(%(expressions)s, @@session.time_zone, 'UTC')",
-                output_field=models.DateTimeField(),
-            ),
         )
 
 
@@ -550,6 +542,16 @@ class EventExt(Event):
         max_digits=13, decimal_places=4, default=0
     )
     details = models.JSONField(null=True, blank=True)
+    details_timestamp = models.GeneratedField(
+        expression=Func(
+            Func(F("details___ts"), function="FROM_UNIXTIME"),
+            template="CONVERT_TZ(%(expressions)s, @@session.time_zone, 'UTC')",
+        ),
+        output_field=models.DateTimeField(),
+        db_persist=False,
+        verbose_name="Last details fetch",
+    )
+
     registrations = models.JSONField(null=True, blank=True)
 
     def get_absolute_url(self) -> str: