Pass required data to frontend for new group delete modal

What does this MR do and why?

Needed for #397039 and !213582

We are working to align the group and project deletion modals so they look and function the same way. In !213585 (merged) we aligned the modals on the list views. Now we want to do the same thing in Settings -> General -> Advanced. Before we can do this we need to pass some data from the backend to the frontend. To avoid issues with Backwards compatibility across updates this MR adds the needed attributes but does not make any frontend changes. Frontend changes will be made in !213582

References

Screenshots or screen recordings

No visual changes, existing modal still works

Before	After

How to set up and validate locally

1. Go to a group -> Settings -> General -> Advanced
2. Click Delete, modal should open and function correctly

MR acceptance checklist

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