Workflow: Ability to assign to a specific user/group per-document

[madduck]

In the use-case of incoming invoices, these need to be approved by specific people, so as part of the initial validation, the employee needs to be able to assign the document to a specific user that should then have to approve/reject the file before it is finally forwarded to bookkeeping.

In an ideal world, this assignment could even be auto-suggested based on machine-learning in the background…