KeyStatus represents the lifecycle state of an API key. - KEY_STATUS_UNSPECIFIED: Default zero value. Never returned by the server. Treated as ACTIVE for backward compatibility but should not be relied on. - KEY_STATUS_ACTIVE: The key is valid and can be used to authenticate. - KEY_STATUS_REVOKED: The key was revoked. Verification fails with VERIFICATION_ERROR_REVOKED. See revocation_reason for the cause. - KEY_STATUS_EXPIRED: The key passed its expire_time. Verification fails with VERIFICATION_ERROR_EXPIRED. The transition is computed at read time and not persisted.