Fix: clamp mailrule max age before migration

docs/migration-v3.md

@@ -326,3 +326,11 @@ behind a reverse proxy may need to set
 [`PAPERLESS_TRUSTED_PROXIES`](configuration.md#PAPERLESS_TRUSTED_PROXIES),
 [`PAPERLESS_ALLAUTH_TRUSTED_CLIENT_IP_HEADER`](configuration.md#PAPERLESS_ALLAUTH_TRUSTED_CLIENT_IP_HEADER),
 or both, to avoid `403 Forbidden` errors on login.
+
+## Database Migrations
+
+Some integer fields have been changed to smaller types to reduce database size. If you have any `MailRule` records with a `maximum_age` greater than 32767, they will be clamped to 32767 during the migration to avoid errors during migration.
+
+### Action Required
+
+No user action is required. The migration will automatically clamp any `MailRule.maximum_age` values greater than 32767 to 32767 during the migration process.

src/paperless_mail/migrations/0002_optimize_integer_field_sizes.py

@@ -4,6 +4,12 @@ from django.db import migrations
 from django.db import models
 
 
+def clamp_mailrule_maximum_age(apps, schema_editor):
+    # Clamp the maximum_age field of MailRule because of PositiveIntegerField --> PositiveSmallIntegerField
+    MailRule = apps.get_model("paperless_mail", "MailRule")
+    MailRule.objects.filter(maximum_age__gt=32767).update(maximum_age=32767)
+
+
 class Migration(migrations.Migration):
     dependencies = [
         ("paperless_mail", "0001_squashed"),
@@ -112,6 +118,10 @@ class Migration(migrations.Migration):
                 verbose_name="consumption scope",
             ),
         ),
+        migrations.RunPython(
+            clamp_mailrule_maximum_age,
+            migrations.RunPython.noop,
+        ),
         migrations.AlterField(
             model_name="mailrule",
             name="maximum_age",