Get Onboarding/Offboarding Tasks and send them to the responsible person

I want to retrieve the task list when a user is set to onboarding/offboarding and send them as notification via slack to the responsible person. Currently we only get these kind of information about the status of "my tasks" only via mail, but want to change this to slack. Unfortunately I haven't found a way to do this in the settings, so I want to try it via API.

Is something like this possible?
KR Hannes