This commit allows the user to drag and drop a record (hierarchy
node) into another one to set the one hovered as the manager of the
one dragged. It also allows to drag a record into a row to define
the manager of the row as the manager of the record dragged.
This commit also adds an new attribute on `hierarchy` tag to use
when we define that view for a certain model to enable the drag and
drop feature.
task-3376776
Xavier Bol (xbo)
2f463b564b