Character-Auth is now correctly a M2M relationship.

test_oauth/migrations/0001_initial.py

@@ -40,7 +40,7 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='character',
             name='auth',
-            field=models.ForeignKey(related_name='characters', to=settings.AUTH_USER_MODEL),
+            field=models.ManyToManyField(related_name='characters', to=settings.AUTH_USER_MODEL, db_index=True),
             preserve_default=True,
         ),
     ]

test_oauth/models.py

@@ -6,7 +6,7 @@ class Character(models.Model):
     id = models.BigIntegerField(primary_key=True)
     name = models.CharField(max_length=128)
 
-    auth = models.ForeignKey(
+    auth = models.ManyToManyField(
         settings.AUTH_USER_MODEL,
         db_index=True,
         related_name='characters'