Clarify where the artifacts metadata .gz is generated

doc/administration/job_artifacts.md

@@ -142,9 +142,9 @@ and [projects APIs](../api/projects.md).
 ## Implementation details
 When GitLab receives an artifacts archive, an archive metadata file is also
-generated. This metadata file describes all the entries that are located in the
-artifacts archive itself. The metadata file is in a binary format, with
-additional GZIP compression.
+generated by [GitLab Workhorse]. This metadata file describes all the entries
+that are located in the artifacts archive itself.
+The metadata file is in a binary format, with additional GZIP compression.
 GitLab does not extract the artifacts archive in order to save space, memory
 and disk I/O. It instead inspects the metadata file which contains all the