Add the ability in the API to remove a translated field from a product

[monsieurtanuki]

What

• For some reason, there may be a translation that has nothing to do here (e.g. a product name translated in English, but it was a typo as the language has no translation in English and the user meant a translation in another language).

We should be able to remove it

• for consistency (e.g. no corrupted English product name translation here)
• and for side effects (e.g. the English product name taking precedency, it becomes the de facto translation for other languages as product_name).

We cannot remove a translation today: if we put an empty string the translation becomes a "populated" empty string.
I also tried to put explicitly a null value instead of an empty string, but got rejected by /cgi/product_jqm2.pl: "Could not save product - null".

To Reproduce

Affected tags:

• 'product_name_'
• 'ingredients_text_'
• 'packaging_text_'

Affected product:

• OK - French version with a translation - https://fr.openfoodfacts.org/produit/3760091722508/chocolat-noir-85-madagascar-ethiquable
• OK - Spanish version with a translation - https://es.openfoodfacts.org/producto/3760091722508/chocolate-negro-de-madagascar-85-cacao-ethiquable
• ko - Italian version with no translation and an empty product name - https://it.openfoodfacts.org/product/3760091722508/ethiquable

No "product_name" for the Italian version, and an empty translation for English:
https://it.openfoodfacts.org/api/v3/product/3760091722508?fields=product_name,product_name_languages&lc=it

{
	"code": "3760091722508",
	"errors": [],
	"product": {
		"product_name_languages": {
			"en": "",
			"es": "Chocolate negro Madagascar 85% cacao",
			"fr": "Chocolat noir 85% de Madagascar"
		}
	},
	"result": {
		"id": "product_found",
		"lc_name": "Prodotto trovato",
		"name": "Product found"
	},
	"status": "success",
	"warnings": []
}

Expected behavior

• we should be able to remove a translation
• I also expected a default translation in product_name, like the English or the first translation available

Type of device

REST-API

Part of

• Multi-lingual products (Tracker) #8049
• 🤳🥫 Support our mobile app (Tracker) #8919

[github-actions]

This issue is stale because it has been open 90 days with no activity.

[github-actions]

This issue has been open 90 days with no activity. Can you give it a little love by linking it to a parent issue, adding relevant labels and projets, creating a mockup if applicable, adding code pointers from https://github.com/openfoodfacts/openfoodfacts-server/blob/main/.github/labeler.yml, giving it a priority, editing the original issue to have a more comprehensive description… Thank you very much for your contribution to 🍊 Open Food Facts