### Cached activation flags for secrets sync on follower nodes are not updated

#### Affected versions

- 1.16.0 - 1.16.2
- 1.17.0 - 1.17.5

#### Issue

Vault 1.16 introduced secrets sync with a one-time flag required to activate the
feature before use. Writing the activation flag to enable secrets sync is forwarded
to leader nodes for storage and distributed to follower nodes, but the in-memory
cache for this flag is not updated on the followers. 

This prevents any secrets sync endpoints (those starting with `sys/sync/`) from
being usable on follower nodes in a cluster.

#### Workaround

The cache is force-updated on all nodes when the leader node steps down and the
cluster promotes a new leader. First, activate the secrets sync feature as described
in the [documentation](/vault/docs/sync#activating-the-feature). Then, have the leader node
step down.
