YARN-7986. ATSv2 REST API queries do not return results for uppercase application tags. Contributed by Charan Hebri.

(cherry picked from commit 75fc05f369929db768b767d79351bca8c13ad9ba)
(cherry picked from commit 91791a8abdf3d46278ee7c15eeb3dddc43918742)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/TimelineServiceV2.md

@@ -486,6 +486,8 @@ You can provide the flow context via YARN application tags:
 
     appContext.setApplicationTags(tags);
 
+Note : The Resource Manager converts YARN application tags to lowercase before storing them. Hence one should convert
+Flow names and Flow versions to lowercase before using them in REST API queries.
 
 ## Timeline Service v.2 REST API