fix(docs): update changelog and add logging.adoc page

Author: razvan

CHANGELOG.md

@@ -13,8 +13,10 @@ All notable changes to this project will be documented in this file.
 - Various documentation of the CRD ([#319]).
 - [BREAKING] Removed version field. Several attributes have been changed to mandatory. While this change is
   technically breaking, existing Spark jobs would not have worked before as these attributes were necessary ([#319]).
-- [BREAKING] Remove `userClassPathFirst` properties from `spark-submit` and all references to the
-  `/stackable/spark/extra-jars` folder. This PR is paired with the `docker-images` PR #556 which removes that folder. ([#355])
+- [BREAKING] Remove `userClassPathFirst` properties from `spark-submit`. This is an experimental feature that was
+  introduced to support logging in xml format. The side-effect of this removal is that the vector agent cannot
+  aggregate output from the `spark-submit` containers. On the other side, it enables dynamic provisionining of
+  delta.io packages (among others) with Stackable stock images which is much more important. ([#355])
 
 ### Fixed
 

docs/modules/spark-k8s/pages/usage-guide/logging.adoc

@@ -0,0 +1,5 @@
+= Logging
+
+Logs produced by SparkApplications are automatically collected by vector agents and can be aggregated as described in xref:concepts:logging.adoc[roles]
+
+NOTE: Only logs produced by the application's driver and executors are collected. Logs produced by `spark-submit` are discarded.