stages/authenticator_totp: fix API validation error due to choices (#…

…7608)

authentik/stages/authenticator_totp/api.py

@@ -1,6 +1,7 @@
 """AuthenticatorTOTPStage API Views"""
 from django_filters.rest_framework.backends import DjangoFilterBackend
 from rest_framework import mixins
+from rest_framework.fields import ChoiceField
 from rest_framework.filters import OrderingFilter, SearchFilter
 from rest_framework.permissions import IsAdminUser
 from rest_framework.serializers import ModelSerializer
@@ -9,12 +10,18 @@
 from authentik.api.authorization import OwnerFilter, OwnerPermissions
 from authentik.core.api.used_by import UsedByMixin
 from authentik.flows.api.stages import StageSerializer
-from authentik.stages.authenticator_totp.models import AuthenticatorTOTPStage, TOTPDevice
+from authentik.stages.authenticator_totp.models import (
+    AuthenticatorTOTPStage,
+    TOTPDevice,
+    TOTPDigits,
+)
 
 
 class AuthenticatorTOTPStageSerializer(StageSerializer):
     """AuthenticatorTOTPStage Serializer"""
 
+    digits = ChoiceField(choices=TOTPDigits.choices)
+
     class Meta:
         model = AuthenticatorTOTPStage
         fields = StageSerializer.Meta.fields + ["configure_flow", "friendly_name", "digits"]