As an approver I want to know when I'm about to create duplicate tasks

[goose-life]

e.g. https://edit.laws.africa/works/akn/za/act/2017/8/revisions/ and https://edit.laws.africa/works/akn/za/act/2017/8/related/ — each time the work was re-approved a bunch of duplicate tasks were created and had to be cancelled.
It's still safer to create duplicate tasks than it is to run the risk of not creating a task (we can only check for an existing Amendment task at the given date on a work, but there are often amendments by different works on the same date).
But the person about to approve the work should be made aware of the fact that they'll need to deal with those, or potentially rather approve the one principal work they're focusing on.

[goose-life]

See proposal at #2258