so at a high level: Ory Keto and OpenFGA both make certain compromises on the underlying Zanzibar concept in the name of simplicity or efficiency. For example, OpenFGA has chosen not to support the concept of a "Zookie" (ZedToken in SpiceDB parlance), which means that they can't easily solve the New Enemy problem. With SpiceDB, we try very hard to remain faithful to the Zanzibar paper's described capabilities whenever possible. Furthermore, SpiceDB has introduced a number of novel concepts (such as well-typed schema, LookupResources, caveats) that those solutions do not yet provide (caveats) or have adopted after we have introduced them