Allows the viewing of hierarchical models (i.e. parent-child
relationships) directly in a tree view. Simply add the recursive
attribute to the tree tag with `recursive="1"` or `recursive="true"` or
`recursive="True"`.
Parent-child field is autodetected from the model based on the
_parent_name field which is standard in the Odoo ORM.
Currently there is no option for expanding all children, but this may be
added in future versions.
