curl --request POST \
  --url http://localhost/api/v3/products/{product}/variants \
  --header 'Content-Type: application/json' \
  --data '
{
  "title": "<string>",
  "sku": "<string>",
  "price": 123,
  "handle": "<string>",
  "external_id": "<string>",
  "web_url": "<string>",
  "barcode": "<string>",
  "description": "<string>",
  "available_quantity": 123,
  "price_discounted": 123,
  "price_comparison": 123,
  "price_cost": 123,
  "position": 123,
  "meta": [
    "<string>"
  ],
  "tags": [
    "<string>"
  ],
  "images": [
    {
      "url": "<string>",
      "sort_order": 123
    }
  ],
  "options": [
    {
      "value": "<string>",
      "name": "<string>",
      "sort_order": 123
    }
  ]
}
'

{
  "data": {
    "id": 123,
    "product_id": 123,
    "sku": "<string>",
    "external_id": "<string>",
    "barcode": "<string>",
    "web_url": "<string>",
    "handle": "<string>",
    "title": "<string>",
    "description": "<string>",
    "position": 123,
    "price": 123,
    "price_discounted": 123,
    "price_comparison": 123,
    "price_cost": 123,
    "available_quantity": 123,
    "images": "<string>",
    "meta": [
      "<unknown>"
    ],
    "tags": [
      "<string>"
    ],
    "options": [
      {
        "name": "<string>",
        "value": "<string>",
        "sort_order": 123
      }
    ],
    "created_at": "<string>",
    "updated_at": "<string>"
  }
}