Add support for chunking in get and set_fields

[boba-and-beer]

When chunking, we need to add support for get_field and set_field using the following schema:
get_field('doc.0.product_id') -> should return the first chunk whereas get_field('doc.1.product_id') should return the second chunk.
('doc.product_id') if exists within a chunk should return a list of values from the chunks.