Introduce feature for PATCH-ing settings of a whole usergroup at once

[tcompa]

(this will be included in fractal-server >=2.7.0a6)

We already expose the PATCH /auth/users/{user_id}/settings/ endpoint, in the webclient page http://localhost:5173/v2/admin/users/{user_id}/edit.

The new endpoint PATCH /auth/group/{user_group_id}/user-settings/ will accept the same kind of request body, and it will apply the PATCH to all users of a that user group.

I think the right place for including this UI is http://localhost:5173/v2/admin/groups/{user_group_id}/edit. We can re-use the same edit-settings form of http://localhost:5173/v2/admin/users/{user_id}/edit, but let's add a small informative message on top of it (on the line of: "Warning: this PATCH will be applied to all the {N} users of this user group"

Additional detail: the new endpoint has a response without body.

[tcompa]

2.7.0a6 now available