Conversion of the lunch kanban model to a proper search extension.
Now that the view search model supports model extensions, it has become
more convenient to provide additional domain informations by appending
new extensions.
This is why the lunch "location" logic (locationId and userId) has been
shifted to a new model extension ("Lunch Model Extension") which
provides an additional domain part to the other search extensions.
Part of task 2228968
Co-authored-by: Julien Mougenot <jum@odoo.com>
Co-authored-by: Mathieu Duckerts-Antoine <dam@odoo.com>