NIFI-4683: Add ability to execute Spark jobs and code via Livy

[mattyb149]

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[joewitt]

reviewing

[jomach]

hi Guys, this is a great change ! I know that the concept from nifi does not want it but yeah is life. :)

One question I have what if the Livy server has Kerberos active where can I give it a keytab to the controlerservice ?

[joewitt]

That probably needs to be a new JIRA and improvement.

[mattyb149]

@jomach Does Livy support client-side Kerberos authentication? I thought the Livy Kerberos stuff was a config on the Livy server side to connect to a Kerberized Hadoop cluster?