**Description** As we want to add a new user authentication state (anonymous user), we should update existing Firestore security rules. **Acceptance Criteria** - [ ] Add new Firestore security rules according to the design. - [ ] Test the rules. **Additional context** [Public dashboard design](https://github.com/Flank/flank-dashboard/blob/master/metrics/web/docs/features/public_dashboard/01_public_dashboard.md#design)