In this section of the SpiceDB docs it points out "In the above example, the relationship between a resource and its teams, as well as a team and its members does not need to be stored in the application's database at all." https://authzed.com/docs/spicedb/concepts/relationships#spicedb-only-relationships I'm curious - is that just meant as an interesting factoid or do people actually rely on SpiceDB as a primary store of relational data in production? In addition to using it for access control?