Prevent race condition with duplicate infractions

DRF's `UniqueTogetherValidator` validates uniqueness by querying the
database before running the actual insert. This is not, has not, and
will never be valid, unless you happen to run a single worker, on a
single thread, and your single worker running on a single thread is the
only client for the database, in which case it may be valid. For any
other cases, it's invalid, and it has never been valid. PostgreSQL spits
out an `IntegrityError` for us if we have a duplicate entry, and
PostgreSQL is the only valid and correct thing to trust here.

The `UniqueTogetherValidator` is removed, and an existing test case
calling into this validator to check for uniqueness is removed.
Furthermore, to work around a Django quirk, `transaction.atomic()` is
added to prevent one `subTest` from messing with another.

Closes #665.

1 files changed, 0 insertions, 7 deletions

diff --git a/pydis_site/apps/api/serializers.py b/pydis_site/apps/api/serializers.py
index 4a702d61..745aff42 100644
--- a/pydis_site/apps/api/serializers.py
+++ b/pydis_site/apps/api/serializers.py
@@ -156,13 +156,6 @@ class InfractionSerializer(ModelSerializer):
             'hidden',
             'dm_sent'
         )
-        validators = [
-            UniqueTogetherValidator(
-                queryset=Infraction.objects.filter(active=True),
-                fields=['user', 'type', 'active'],
-                message='This user already has an active infraction of this type.',
-            )
-        ]
 
     def validate(self, attrs: dict) -> dict:
         """Validate data constraints for the given data and abort if it is invalid."""