providers/saml: fix 500 when SAML Provider not assigned to application

passbook/providers/app_gw/models.py

@@ -1,13 +1,16 @@
 """passbook app_gw models"""
 import string
 from random import SystemRandom
+from typing import Optional
 
 from django.db import models
+from django.http import HttpRequest
 from django.utils.translation import gettext as _
 from oidc_provider.models import Client
 
 from passbook import __version__
 from passbook.core.models import Provider
+from passbook.lib.utils.template import render_to_string
 
 
 class ApplicationGatewayProvider(Provider):
@@ -21,13 +24,13 @@ class ApplicationGatewayProvider(Provider):
 
     form = "passbook.providers.app_gw.forms.ApplicationGatewayProviderForm"
 
-    def html_setup_urls(self, request):
+    def html_setup_urls(self, request: HttpRequest) -> Optional[str]:
         """return template and context modal with URLs for authorize, token, openid-config, etc"""
         cookie_secret = "".join(
             SystemRandom().choice(string.ascii_uppercase + string.digits)
             for _ in range(50)
         )
-        return (
+        return render_to_string(
             "app_gw/setup_modal.html",
             {"provider": self, "cookie_secret": cookie_secret, "version": __version__},
         )