inventory plugin "group_by: region" should not display sites as childeren while looking for devices

[LuPo]

Hello community. I want to submit the following issue for the inventory plugin. While I am looking for devices to be grouped by the region in which it's site is located, I expect to have inventory groups (regions) being populated with hosts (devices). Instead I see all the possible sites flattened as child groups of the main groups (defined by regions). It is rather problematic as even empty groups (sites) without devices (based on the filter applied to the query) are cluttering the overall view of groups. I have almost 600 sites and it does not see all of them as groups here. Otherwise, if I needed it, I would have chosen group_by: sites.

I see the issue in the main() function definition where the following condition is set:

    if (
        site_group_by in self.group_by
        or "location" in self.group_by
        or "region" in self.group_by
        or "site_group" in self.group_by
    ):
        self._add_site_groups()

this is immediately followed by:

    # Create groups for regions, containing the site groups
    if "region" in self.group_by:
        self._add_region_groups()

The point here should not be to add site groups to the regions though. Especially while I am looking to create a device inventory.
I understand that we have to extract site from the device and than get the region from the site, this is why in my opinion we need to rewrite _add_region_group() and not treat group_by: region to look first for all the available sites. The possible approach could be to find sites which has devices we are looking for. Subsequently, for each of these sites, find a region and assign host to it as a group.