When team is removed do not delete webhooks belonging to it (#3873)

# What this PR does
When a team is deleted webhooks belonging to that team will be marked as
having no team instead of the webhook being deleted.

## Which issue(s) this PR fixes

## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - Check for permissions on Slack escalate command ([#3891](https://github.com/grafana/oncall/pull/3891))
+- Do not delete webhook if its team is deleted @mderynck ([#3873](https://github.com/grafana/oncall/pull/3873))
 
 ## v1.3.105 (2024-02-13)
 

engine/apps/webhooks/migrations/0012_alter_webhook_team.py

@@ -0,0 +1,20 @@
+# Generated by Django 4.2.10 on 2024-02-14 17:55
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('user_management', '0020_organization_is_grafana_labels_enabled'),
+        ('webhooks', '0011_auto_20230920_1813'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='webhook',
+            name='team',
+            field=models.ForeignKey(default=None, null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='webhooks', to='user_management.team'),
+        ),
+    ]

engine/apps/webhooks/models/webhook.py

@@ -120,7 +120,7 @@ class Webhook(models.Model):
     )
 
     team = models.ForeignKey(
-        "user_management.Team", null=True, on_delete=models.CASCADE, related_name="webhooks", default=None
+        "user_management.Team", null=True, on_delete=models.SET_NULL, related_name="webhooks", default=None
     )
 
     user = models.ForeignKey(

engine/apps/webhooks/tests/test_webhook.py

@@ -304,3 +304,19 @@ def test_escaping_unicode_in_string(make_organization, make_custom_webhook, data
     }
     request_kwargs = webhook.build_request_kwargs(payload)
     assert request_kwargs == {"headers": {}, **expected_kwargs}
+
+
+@pytest.mark.django_db
+def test_webhook_not_deleted_with_team(make_organization, make_team, make_custom_webhook):
+    organization = make_organization()
+    team = make_team(organization=organization)
+    webhook = make_custom_webhook(
+        organization=organization,
+        team=team,
+    )
+    assert webhook.team == team
+    webhook_pk = webhook.pk
+    team.delete()
+
+    webhook = Webhook.objects.get(pk=webhook_pk)
+    assert webhook.team is None