Before implementing [[ https://docs.softwareheritage.org/devel/swh-storage/extrinsic-metadata-specification.html | the metadata spec ]], we need to know where to implement it in; so we need to decide where to store it.
I see three options:
* in the main swh-storage, which may cause some issues scaling
* implemented in swh-storage, but running on a different postgres/cassandra cluster, which might be confusing
* implemented in a new component entirely, which adds some complexity and code duplication with swh-storage if we decide to use postgres or cassandra