only-if-cached behavior

Author: kriszyp

docs/technical-details/release-notes/4.tucker/4.6.0.md

@@ -22,3 +22,6 @@ An important change is that logging to standard out/error will _not_ include the
 
 ### Resource API Upgrades
 4.6 includes an upgraded form of the Resource API that can be selected with significant improvements in ease of use.
+
+### only-if-cached behavior
+Previously when the `only-in-cached` caching directive was used and the entry was not cached, Harper would return a 504, but still make a request to origin in the background. Now, Harper will no longer a request to origin for `only-if-cached`.