curl --location --request POST 'https://demo.myshopify.com//admin/api//blogs//metafields.json'
{
"metafield": {
"id": 1069228998,
"namespace": "my_fields",
"key": "sponsor",
"value": "Shopify",
"description": null,
"owner_id": 382285388,
"created_at": "2023-01-03T12:52:48-05:00",
"updated_at": "2023-01-03T12:52:48-05:00",
"owner_resource": "blog",
"type": "single_line_text_field",
"admin_graphql_api_id": "gid://shopify/Metafield/1069228998"
}
}