move backoffice.tokens into core

src/backoffice/views/auth.py

@@ -19,9 +19,9 @@ from django_ratelimit.decorators import ratelimit
 
 from core.models import PlatformUser, UserCommunicationChannel
 from core.forms import PasswordResetForm
+from core.tokens import channel_activation_token
 
 from ..forms import SignUpForm, LoginForm
-from ..tokens import channel_activation_token
 from .mixins import ConferenceMixin, PasswordMixin