CSV-Export does not work when form block is nested #86
Description
What?
When the form block is for example within an columns block from https://github.com/eea/volto-columns-block, submitted data can be displayed within the UI but the CSV export throws an AttributeError.
Fix
Can be fixed by using get_blocks from utils.py like it is already done in the FormData class: https://github.com/collective/collective.volto.formsupport/blob/main/src/collective/volto/formsupport/restapi/services/form_data/form_data.py#L85
Works because get_blocks takes care of finding nested form blocks as well.