```release-note:feature
**Strong Consistency Control**: Support `X-Vault-Index` and `X-Vault-Inconsistent` headers to ensure client/server consistency.
  - `X-Vault-Index` is now sent when a write is performed.
  - The `X-Vault-Inconsistent` request header can take the following values to control the fallback behavior when the node is out of date:
      - `fail`, to respond with 429 Too Many Requests and a `Retry-After` value,
      - `forward-active-node` to forward the request to the active node, or
      - `await-state` to hold the request locally to attempt to catch up, optionally falling back to one of the above behaviors (if also specified) or the server default.
  - On listeners, three new configuration parameters are now respected:
      - `consistency_fallback_behavior` to set the default fallback for `await-state`,
      - `consistency_missing_header_forward` to automatically forward requests which do not have any consistency control headers, and
      - `consistency_max_index_wait` to indicate the maximum amount of time `await-state` should pause before forwarding the request.
```
```release-note:improvement
core/server: Support storage-indicated index values in Server Side Consistent Tokens (SSCTs), improving their utility. Previously these tokens always had an index value of `0`.
```
```release-note:bug
core/server: Add missing `disable_ssct_token` parameter to support enabling SSCTs.
```
