For configurable products, there is a section to select the options and allow to choose one product variant.
This spec corresponds to the first version of the feature as an MVP. Future version will add more complex UI and behavior.

configurable.configurableAttrs, that holds an array of attribute Ids.string attributes that has inclusion validation to have a limited possible values."" and title "Select an option".All possible values are listed in the dropdowns, no matter the existence of variants for the configurable product.
By default, the empty option is selected.
When adding to cart, all dropdowns must have a non-empty option selected.
The configurable cart items must include the selected options in the field variantOptions.
Integration:
varianOptions field is an object of the form:{
"attr Id 1": "selected attr value 1",
"attr Id 2": "selected attr value 2",
...
"attr Id n": "selected attr value n",
}
For example:
{
"00de4b03-b2d7-4597-a11f-88b9d97d9f03": "36",
"f82e0ddb-f297-40e4-b4ba-b068b2f216a9": "cian",
}
Where 00de4b03-b2d7-4597-a11f-88b9d97d9f03 and f82e0ddb-f297-40e4-b4ba-b068b2f216a9 would be the attribute Ids for size and color.