set id field type independent of DEFAULT_AUTO_FIELD

see https://docs.djangoproject.com/en/3.2/topics/db/models/#automatic-primary-key-fields

mfa/migrations/0004_alter_mfakey_id.py

@@ -0,0 +1,17 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("mfa", "0003_alter_mfakey_method"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="mfakey",
+            name="id",
+            field=models.BigAutoField(
+                primary_key=True, serialize=False, verbose_name="ID"
+            ),
+        ),
+    ]

mfa/models.py

@@ -3,6 +3,7 @@
 
 
 class MFAKey(models.Model):
+    id = models.BigAutoField(primary_key=True, serialize=False, verbose_name='ID')
     user = models.ForeignKey(
         settings.AUTH_USER_MODEL, on_delete=models.CASCADE
     )