curl --request POST \
  --url https://api.app.lastaccountingcompany.com/portal/invoices/{invoice_id}/send \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "customer_id": "<string>"
}
'

{
  "id": "<string>",
  "status": "<string>",
  "delivery_channel": "<string>",
  "customer": {
    "name": "<string>",
    "id": "<string>",
    "business_id": "<string>",
    "vat_number": "<string>",
    "address_line1": "<string>",
    "postal_code": "<string>",
    "city": "<string>",
    "country_code": "<string>",
    "email": "<string>",
    "einvoice_address": "<string>",
    "einvoice_operator": "<string>",
    "default_payment_terms_days": 123,
    "default_vat_code": "<string>",
    "default_vat_rate_basis_points": 123,
    "default_invoice_language": "<string>"
  },
  "lines": [
    {
      "description": "<string>",
      "quantity": "<string>",
      "unit_price_cents": 123,
      "net_cents": 123,
      "vat_cents": 123,
      "gross_cents": 123,
      "vat_rate_basis_points": 123,
      "vat_code": "<string>"
    }
  ]
}