Add view for linking persons to users
Add a view that does the following:
- Show a table that has one column with all persons, and one column with a select box for existing users
- Allow selecting the user account belonging to each person
You should use a ModelFormSet (see BiscuIT-App-Alsijil on how to get a mostly automated formset listing persons).
In a second step, add a way to get the same view, but only showing persons that do not have a user account linked.