For now, this is not even computed by all oracles. Only a script running on mine. This is currently a centralized architecture and I have no short term plan to make it easier to replicate. The binary comes from the hugo/distance-precompute branch.
As indexers are designed, I don’t think it is a good idea to add external data to it. It would be better to serve this directly on a part of Duniter RPC API. However, not all Duniter nodes would have this plugin installed (like not v1 Duniter nodes have transaction indexing, g1-monit, or wotwizard installed). So there should be a way to know which services are available where.
Client software must know a large list of URLs kinds (see Liste des endpoints topic). The same problem is valid for rpc endpoints, squid endpoints, datapod endpoints…