update changelog

CHANGELOG.md

@@ -6,6 +6,25 @@ See also the [GitHub releases page](https://github.com/FriendsOfSymfony/FOSHttpC
 3.x
 ===
 
+3.1.0
+-----
+
+### Symfony HttpCache
+
+* Add events `PRE_FORWARD` and `POST_FORWARD` to allow event listeners to alter
+  the request before and after it is sent to the backend.
+* Changed CustomTtlListener to use the `POST_FORWARD` event instead of
+  `PRE_STORE`. Using `PRE_STORE`, requests that are not considered cacheable by
+  Symfony were never cached, even when they had a custom TTL header.
+* Add flag `fallbackToSmaxage` to `CustomTtlListener` to allow controlling
+  fallback to `s-maxage` if custom TTL header is not defined on the response.
+* Fix: Do not call store if Response object is not longer cacheable after event
+  listeners. If you use the custom TTL system, this is only a performance
+  improvement, because the TTL of the response would still be 0. With a custom
+  listener that changes the response explicitly to not be cached but does not
+  change `s-maxage`, this bug might have led to caching responses that should not
+  have been cached.
+
 3.0.0
 -----