Use shorter user ID's for now

Can undo this when MasterKale/SimpleWebAuthn#530 is fixed

_app/homepage/services/registration.py

@@ -1,4 +1,5 @@
 from typing import Union, List, Optional
+import secrets
 
 from django.conf import settings
 from webauthn import (
@@ -110,6 +111,8 @@ def generate_registration_options(
             rp_id=settings.RP_ID,
             rp_name=settings.RP_NAME,
             user_name=username,
+            # TODO: Remove when https://github.com/MasterKale/SimpleWebAuthn/issues/530 gets fixed
+            user_id=secrets.token_bytes(32),
             attestation=_attestation,
             authenticator_selection=authenticator_selection,
             supported_pub_key_algs=supported_pub_key_algs,