Set spark.scheduler.pool to authenticated user name

Setting spark.scheduler.pool to authenticated user name would allow to have multiple resource pools for different users when using shared Spark context / shared Spark Interpreter;

This improvement request is for "The interpreter will be instantiated Globally in shared process" Spark Interpreter mode.
 
Per Spark documentation, https://spark.apache.org/docs/latest/job-scheduling.html 
 

" within each Spark application, multiple “jobs” (Spark actions) may be running concurrently if they were submitted by different threads 
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threads. By “job”, in this section, we mean a Spark action (e.g. save, collect) and any tasks that need to run to evaluate that action. Spark’s scheduler is fully thread-safe and supports this use case to enable applications that serve multiple requests (e.g. queries for multiple users).
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Without any intervention, newly submitted jobs go into a default pool, but jobs’ pools can be set by adding the spark.scheduler.pool “local property” to the SparkContext in the thread that’s submitting them.    "

Notice that setting spark.scheduler.pool to authenticated user name has to be done in a separate thread - assuming Zeppelin internally has a separate thread for each separate authenticated user..