keystone_authtoken/auth_uri is deprecated [1] and replaced by www_authenticate_uri. The bug has also been raised on the launchpad [2] to remove auth_uri from Openstack Cinder Charm which is dependant on charm-helpers code.

[1] https://review.opendev.org/c/openstack/keystonemiddleware/+/508522/
[2] https://bugs.launchpad.net/charm-cinder/+bug/1837119