Show the creation date of hippo requests in the TODO list

Currently the editors are unable to see when workflow requests (e.g. publication requests) are created. It would be nice to be able to see when the requests were created (how old they are).

The creation date is currently unavailable. This creation date will be provided in the repository (see REPO-1400). When the creation date is available, it would be nice to show this date in the TODO list.