Hi Lorena Gascon,
If my understanding is correct ,your userTask will be used from BPM process step. If so , once you deploy (build/upload) your code you can find two service generated in BPM package with name as taskName_InputMapService & taskName_OutputMapService. This two service will get invoked when task is assigned from BPM flow and when task is completed. So, you can put your custom logic in this two step.
Thanks!
Baharul Islam
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