Handle unique validator in DRF, not Django.

I was handling this in a Django vanilla kind of way, which was causing
the constraint to return a 500 instead of a 400. This changes the
approach to use the DRF way, and makes it return 400.

It doesn't actually change the way anything behaves, other than
returning the right status code.

3 files changed, 15 insertions, 15 deletions

diff --git a/pydis_site/apps/api/migrations/0057_create_new_filterlist_model.py b/pydis_site/apps/api/migrations/0057_create_new_filterlist_model.py
index 44025ee8..b5398568 100644
--- a/pydis_site/apps/api/migrations/0057_create_new_filterlist_model.py
+++ b/pydis_site/apps/api/migrations/0057_create_new_filterlist_model.py
@@ -25,9 +25,5 @@ class Migration(migrations.Migration):
                 ('comment', models.TextField(help_text="Optional comment on this entry.", null=True)),
             ],
             bases=(pydis_site.apps.api.models.mixins.ModelReprMixin, models.Model),
-        ),
-        migrations.AddConstraint(
-            model_name='filterlist',
-            constraint=models.UniqueConstraint(fields=('content', 'type'), name='unique_filter_list'),
         )
     ]
diff --git a/pydis_site/apps/api/models/bot/filter_list.py b/pydis_site/apps/api/models/bot/filter_list.py
index d279e137..5961aed7 100644
--- a/pydis_site/apps/api/models/bot/filter_list.py
+++ b/pydis_site/apps/api/models/bot/filter_list.py
@@ -28,14 +28,3 @@ class FilterList(ModelTimestampMixin, ModelReprMixin, models.Model):
         help_text="Optional comment on this entry.",
         null=True
     )
-
-    class Meta:
-        """Metaconfig for this model."""
-
-        # This constraint ensures only one filterlist with the
-        # same content can exist. This means that we cannot have both an allow
-        # and a deny for the same item, and we cannot have duplicates of the
-        # same item.
-        constraints = [
-            models.UniqueConstraint(fields=['content', 'type'], name='unique_filter_list'),
-        ]
diff --git a/pydis_site/apps/api/serializers.py b/pydis_site/apps/api/serializers.py
index 8fd40da7..54bb8a5d 100644
--- a/pydis_site/apps/api/serializers.py
+++ b/pydis_site/apps/api/serializers.py
@@ -113,6 +113,21 @@ class FilterListSerializer(ModelSerializer):
         model = FilterList
         fields = ('id', 'created_at', 'updated_at', 'type', 'allowed', 'content', 'comment')
 
+        # This validator ensures only one filterlist with the
+        # same content can exist. This means that we cannot have both an allow
+        # and a deny for the same item, and we cannot have duplicates of the
+        # same item.
+        validators = [
+            UniqueTogetherValidator(
+                queryset=FilterList.objects.all(),
+                fields=['content', 'type'],
+                message=(
+                    "A filterlist for this item already exists. "
+                    "Please note that you cannot add the same item to both allow and deny."
+                )
+            ),
+        ]
+
 
 class InfractionSerializer(ModelSerializer):
     """A class providing (de-)serialization of `Infraction` instances."""