Complete invoice call validation feature

counter/migrations/0033_invoicecall.py

@@ -1,4 +1,4 @@
-# Generated by Django 5.2.3 on 2025-09-09 10:24
+# Generated by Django 5.2.3 on 2025-10-15 21:54
 
 import django.db.models.deletion
 from django.db import migrations, models
@@ -9,7 +9,7 @@ import counter.models
 class Migration(migrations.Migration):
     dependencies = [
         ("club", "0014_alter_club_options_rename_unix_name_club_slug_name_and_more"),
-        ("counter", "0031_alter_counter_options"),
+        ("counter", "0032_scheduledproductaction"),
     ]
 
     operations = [
@@ -40,6 +40,12 @@ class Migration(migrations.Migration):
             options={
                 "verbose_name": "Invoice call",
                 "verbose_name_plural": "Invoice calls",
+                "constraints": [
+                    models.UniqueConstraint(
+                        fields=("club", "month"),
+                        name="counter_invoicecall_unique_club_month",
+                    )
+                ],
             },
         ),
     ]