Support for Group Header Slot in ui_template

### Description

It would be cool if we could utilize the group-by feature in the template node when creating a data table via template, which is described at https://vuetifyjs.com/en/components/data-tables/basics/#group-header-slot.

When adding the example code of this to a template, the rows are non-expandable:

Within the console, the following error is shown:

So I understand that it might be a module that needs updating? Thanks in advance, and sorry if any details are missing :)

### Have you provided an initial effort estimate for this issue?

I am no FlowFuse team member