Include child locations in rack/device lists for location floorplans

[bpapaylle]

Problem

When a floorplan is attached to a parent location, the rack and device
pick-lists in the editor filter on an exact location match
(location=fp_instance.location.id). Racks are usually assigned to leaf
locations (rooms, rows), so a floorplan on the parent location offers
nothing to place.

Typical case: a datacenter location split into several room locations,
with every rack assigned to a room. The datacenter-level floorplan shows
an empty rack list, making a global datacenter view impossible.

Solution

Filter on the location's descendants instead of an exact match, in both
FloorplanRackListView and FloorplanDeviceListView:

location__in=fp_instance.location.get_descendants(include_self=True)

Location is a tree model, so get_descendants(include_self=True) is
available natively. Leaf locations keep the exact same behaviour as
before (include_self=True, no descendants), so this is strictly
additive: only parent-location floorplans gain the racks/devices of
their children.

Tested

On NetBox 5.0.1, with a parent location whose racks all live in child
locations: before the change, the parent-location floorplan offered no
racks at all; after, every rack from the child locations is offered,
and child-location floorplans behave exactly as before.

🤖 Generated with Claude Code

[cruse1977]

Interesting tested on NetBox 5.0.1 - given that doesn't exist.

[bpapaylle]

it's a typo my bad, it was tested on the following docker image netboxcommunity/netbox:v4.6.2-5.0.1, that is where the 5.0.1 is coming from.