Update changelog

Author: danielballan

CHANGELOG.md

@@ -8,6 +8,8 @@ Write the date in place of the "Unreleased" in the case a new version is release
 ### Added
 
 - `docker-compose.yml` now uses the healthcheck endpoint `/healthz`
+- In client, support specifying API key expiration time as string with
+  units, like ``"7d"` or `"10m"`.
 
 ### Fixed