GHSA-68m9-983m-f3v5: OpenFGA: Unauthenticated playground endpoint discloses preshared API key in HTML response

When OpenFGA is configured to use preshared-key authentication with the built-in playground enabled, the local server includes the preshared API key in the HTML response of the /playground endpoint. The /playground endpoint is enabled by default and does not require authentication. It is intended for local development and debugging and is not designed to be exposed to production environments.