Add support for Weight of one empty unit (g)and Quantity of product contained per unit

[teolemon]

What

• Add support for Weight of one empty unit (g)and Quantity of product contained per unit

    > Great for the quick turnaround @monsieurtanuki 👏 Are `Weight of one empty unit (g)`and `Quantity of product contained per unit` causing any issues ?
  

They are not in off-dart.

Originally posted by @monsieurtanuki in openfoodfacts/smooth-app#3475 (comment)

[monsieurtanuki]

Add support for Weight of one empty unit (g)and Quantity of product contained per unit

@stephanegigandet How can we retrieve/set those values from/to the server?

[stephanegigandet]

@monsieurtanuki

for reading, we have the fields in the packagings array: https://redocly.github.io/redoc/?url=https://raw.githubusercontent.com/openfoodfacts/openfoodfacts-server/packagings-api/docs/reference/api-v3.yml#tag/Read-Requests/operation/get-product-by-barcode

Array 

number_of_units	integerumber of units of this packaging component contained in the product (e.g. 6 for a pack of 6 bottles)
shape	object (shape)The shape property is canonicalized using the packaging_shapes taxonomy.
material	object (material)The material property is canonicalized using the packaging_materials taxonomy.
recycling	object (recycling)The recycling property is canonicalized using the packaging_recycling taxonomy.
quantity_per_unit	stringQuantity (weight or volume) of food product contained in the packaging component. (e.g. 75cl for a wine bottle)
quantity_per_unit_value	numberValue parsed from the quantity field.
quantity_per_unit_unit	stringUnit parsed and normalized from the quantity field.
weight_specified	numberWeight (as specified by the manufacturer) of one unit of the empty packaging component (in grams). (e.g. for a 6 pack of 1.5l water bottles, it might be 30, the weight in grams of 1 empty water bottle without its cap which is a different packaging component).
weight_measured	numberWeight (as measured by one or more users) of one unit of the empty packaging component (in grams). (e.g. for a 6 pack of 1.5l water bottles, it might be 30, the weight in grams of 1 empty water bottle without its cap which is a different packaging component).
weight_estimated	numberWeight (as estimated from similar products) of one unit of the empty packaging component (in grams). (e.g. for a 6 pack of 1.5l water bottles, it might be 30, the weight in grams of 1 empty water bottle without its cap which is a different packaging component).
weight	numberWeight of one unit of the empty packaging component.
weight_source_id	stringIndicates which field was used to populate the "weight" field. Either "specified", "measured", or "estimated"

For writing, each packaging component has a weight_measured and quantity_per_unit fields:
https://github.com/openfoodfacts/openfoodfacts-server/blob/main/docs/reference/schemas/packagings/packaging_component-write.yaml

[monsieurtanuki]

Thank you @stephanegigandet!