message: add cycle recovery
diff: - [RFC 0006: Dynamic database](./rfcs/RFC0006-Dynamic-Databases.md)
  - [RFC 0007: Opinionated cancelation](./rfcs/RFC0007-Opinionated-Cancelation.md)
  - [RFC 0008: Remove garbage collection](./rfcs/RFC0008-Remove-Garbage-Collection.md)
  + - [RFC 0009: Cycle recovery](./rfcs/RFC0009-Cycle-recovery.md)
  # Appendices
  