Context:
With OPT-3085, we added variable reports which allow users to aggregate the data by summing up all the values of a variable. We don't have that feature for process instance/flow node/user task duration reports yet and it would make sense to add the aggregation there as well.

• given:
  • I create a process instance/ user task/ flow node duration report
• when:
  • I go to the configuration popover and select the aggregations
• then:
  • I can select the sum option which will sum up all the values and show the accumulated sum as a result
• such that:
  • I'm able to see how long process instances were running in total for a month to do some cost planning

Hint:

• the CombinedProcessReportResultTest needs to be adjusted as well since we filter out the sum aggregation at the moment.