A stock item is a package unit that defines the formats in which an ingredient can be stored or ordered in. It can also describe the same for a recipe, in the case of stockable recipes.
stockable_recipe must be given, but not both.
stockable_recipe is given, you are defining a package for a stockable recipe. The recipe referenced in this field must be stockable.
PackageDescription object in this endpoint, one of
unit_stock_item must be given, but not both. When
unit_stock_item is given, you are defining this stock item as a multiple of another stock item.
Stock items can be defined in base units (for example g, ml, cl...) but also as units of other stock items. Imagine a Cola that can be purchased as a can (33cl) but also as a pack of 6 cans (therefore 6 units of the base 33cl package).
For clarity, check the examples.