This is a major change in the OCI support, as the format of the OCI image
registries changed. Instead of now having a "ref" file for each image
in the repo it has a single index json file, where the ref name is now
a per-image annotation.
This allows us to support OCI much better, as we can now use the actual
flatpak ref as the OCI ref name, and we can find all the flatpak refs
in a remote.
So, with this you can just use:
flatpak remote-add --oci remote-name URL
and then you can use the regular flatpak operations on the remote.