There are scenarios where a keystone's consumer might want to talk to
keystone over the internal url, exposing this information over the
relation would allow services like openstack-dashboard to implement
a configuration option equivalent to `use-internal-endpoint` provided
by nova-cloud-controller.
Closes-bug: #1812361
Change-Id: I129a686ed9d20035894a36500cb64d1798d3f9d2
Co-Authored-By: Felipe Reyes <felipe.reyes@canonical.com>