When a Geo primary site receives a batch upload request, it will respond
with a URL to itself, rather than a custom clone URL configured in
https://docs.gitlab.com/ee/user/admin_area/settings/visibility_and_access_controls.html#custom-git-clone-url-for-https.
This is safe because it is already required that a Geo primary site be
accessible via its `external_url`, and in fact other parts of the
push-to-secondary request flow already depend on this to work.