Set parent quick action

Release notes

You can now set a parent record via quick actions for work item records (tasks, objectives and key result).

Summary

Given that we have Hierarchy support present for Work Items, we want to expose this functionality via quick actions too.

This issue proposes to add /set_parent quick action for work items, where the syntax would be as follows;

/set_parent <work item #iid, reference, or a URL>

In case current work item (where this quick action is being run) already has a parent associated, this command would simply replace it, but additionally would show a quick action success message like Removed parent item #123 and set new parent item #456, as suggested in &11138 (comment 1566791360).