providers/oauth2: fix nonce field not being optional

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/providers/oauth2/migrations/0016_alter_authorizationcode_nonce.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.2.5 on 2021-07-20 22:32
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("authentik_providers_oauth2", "0015_auto_20210703_1313"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="authorizationcode",
+            name="nonce",
+            field=models.TextField(default=None, null=True, verbose_name="Nonce"),
+        ),
+    ]

authentik/providers/oauth2/models.py

@@ -338,7 +338,7 @@ class AuthorizationCode(ExpiringModel, BaseGrantModel):
     """OAuth2 Authorization Code"""
 
     code = models.CharField(max_length=255, unique=True, verbose_name=_("Code"))
-    nonce = models.TextField(blank=True, default="", verbose_name=_("Nonce"))
+    nonce = models.TextField(null=True, default=None, verbose_name=_("Nonce"))
     is_open_id = models.BooleanField(
         default=False, verbose_name=_("Is Authentication?")
     )