Add capacity to know which fields are producer provided

[teolemon]

Why - Problem description

• We're going to enforce better protection of data when we get reliable data from producers.
• As a result, regular contributors are going to try and edit products, and their contributions won't be saved.
• This has the potential to be a frustrating/confusing experience, so we should prevent it from happening.

What - Proposed solution

• Add capacity to know which fields are producer provided.
• This is provided by the API: https://world.openfoodfacts.org/api/v0/product/7613035982116.json?fields=sources

[monsieurtanuki]

I've just managed to change the product name in French on the prod website for 7613035982116 (and rolled back, of course).
As far as I understand the JSON that name was provided by the manufacturer, right?
But the protection of producer data is not implemented yet on the server side, right?

What are we supposed to store in off-dart? For each field (possibly with language):

1. a bool stating that it was set by the producer?
2. a timestamp (or null) of the latest update by the producer?
3. the sorted lists of timestamps
4. a timestamp + the id of the producer for the latest update?
5. the sorted lists of timestamps + producers?

{
	"code": "7613035982116",
	"product": {
		"sources": [{
			"fields": [
				"product_name_fr",
				"abbreviated_product_name_fr",
				"generic_name_fr",
				"brands",
				"labels",
				"producer_version_id",
				"conservation_conditions_fr",
				"nutriscore_grade_producer",
				"customer_service_fr",
				"preparation_fr",
				"data_sources",
				"serving_size",
				"ingredients_text_fr"
			],
			"id": "org-nestle-france",
			"images": [],
			"import_t": 1679119300,
			"manufacturer": 1,
			"name": "nestle-france",
			"url": null
		}, {
			"fields": [],
			"id": "org-nestle-france",
			"images": [],
			"import_t": 1680150654,
			"manufacturer": 1,
			"name": "nestle-france",
			"url": null
		}, {
			"fields": [],
			"id": "org-nestle-france",
			"images": [],
			"import_t": 1680669259,
			"manufacturer": 1,
			"name": "nestle-france",
			"url": null
		}]
	},
	"status": 1,
	"status_verbose": "product found"
}

[monsieurtanuki]

Duplicate with #956, I think.