fix: 配置仅已存在用户登录后 cas用户首次登录报403 (#8752)

Co-authored-by: feng626 <1304903146@qq.com>

apps/authentication/backends/cas/views.py

@@ -0,0 +1,15 @@
+from django_cas_ng.views import LoginView
+from django.core.exceptions import PermissionDenied
+from django.http import HttpResponseRedirect
+
+__all__ = ['LoginView']
+
+
+class CASLoginView(LoginView):
+    def get(self, request):
+        try:
+            return super().get(request)
+        except PermissionDenied:
+            return HttpResponseRedirect('/')
+
+