Test factory get_deletable_objects needs to check relationships of children of Tree objects

Proposed Changes

nautobot.utilities.testing.utils.get_deletable_objects (in 1.5+) filters a queryset on protected fields fieldname__isnull=True but also needs to check any children of a tree object. If a child’s fieldname is not null, you cannot delete the parent.

Justification

Reuse testing code for testing object deletion

[gsnider2195]

@HanlinMiao try this

from tree_queries.models import TreeNodeForeignKey
from mptt.models import TreeForeignKey

def get_deletable_objects(model, queryset):
    """
    Returns a queryset of objects in the supplied queryset that have no protected relationships that would prevent deletion.
    """
    q = Q()
    for field in model._meta.get_fields(include_parents=True):
        if getattr(field, "on_delete", None) is PROTECT:
            q &= Q(**{f"{field.name}__isnull": True})
        # Only delete leaf nodes of trees to reduce complexity
        if isinstance(field, (TreeForeignKey, TreeNodeForeignKey)):
            q &= Q(**{f"{field.related_query_name()}__isnull": True})
    return queryset.filter(q)

[gsnider2195]

The above suggestion breaks on InventoryItem because the children reverse relationship name is child_items instead of children.