helm: add cronjob to autoclose interactive sessions

[audrium]

closes reanahub/reana-workflow-controller#498

To test update values.yaml with:

interactive_sessions:
  cronjob_schedule: "*/2 * * * *"  # every 2 minutes
  maximum_duration: 0

It will try to auto-close all the sessions every two minutes

[codecov-commenter]

Codecov Report

Merging #693 (5cc8fd4) into master (868775c) will not change coverage.
The diff coverage is n/a.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #693   +/-   ##
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  Coverage   18.84%   18.84%           
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  Files          26       26           
  Lines        2144     2144           
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  Hits          404      404           
  Misses       1740     1740           

Impacted Files	Coverage Δ
reana/reana_dev/run.py	26.72% <ø> (ø)

[audrium]

One possible addition could be to pass maximum_duration value set by administrators down to reana-ui and to enrich the current notification with a message indicating that the session will be closed after a specified number of days. I've quickly checked that it's not feasible to show the notification in the actual jupyter notebook itself, but we could at least inform users in REANA.

Edit: implemented in reanahub/reana-ui#312