Scope folder for images uploaded from the template image picker:
config :phoenix_kit_document_creator, :attachments_parent_folder, {MyApp.Media, :parent_for}called as parent_for(:document_image, actor_uuid, %{template_file_id: id}) (or /2),
returning {:ok, folder_uuid} or nil (no scope, today's behaviour).
The answer is passed to core's media selector as scope_folder, which files
uploads made from the selector under that folder; picking an existing file
does not move it. The hook contract is core's
PhoenixKit.Modules.Storage.ResourceFolders: an answer that is not a uuid,
or a hook that raises, throws or exits, is logged and treated as nil.