Upsert a billing

curl --location --request POST 'https://api.sandbox.neofin.services/billing/' \
--header 'api-key: ' \
--header 'secret-key: ' \
--header 'Content-Type: application/json' \
--data-raw '{
    "billings": [
        {
            "address_city": "São Paulo",
            "address_complement": "CJ 4",
            "address_neighborhood": "Jardim Paulista",
            "address_number": "365",
            "address_state": "SP",
            "address_street": "Rua Pamplona",
            "address_zip_code": "01405-000",
            "amount": 150,
            "by_mail": false,
            "by_whatsapp": true,
            "customer_document": "51491769000190",
            "customer_mail": "teste@company.com",
            "customer_name": "Company Teste LTDA",
            "customer_phone": "+5511987654321",
            "customer_secondary_phone": "",
            "discount_before_payment": 0,
            "discount_before_payment_due_date": 0,
            "description": "Parcela 1/2",
            "due_date": 1678316400,
            "fees": 0,
            "fine": 0,
            "installment_type": "custom",
            "installments": 1,
            "nfe_number": "2121212121212",
            "recipients": [],
            "type": "generic",
            "integration_identifier": "1111a",
            "boleto_base64": "",
            "code": "",
            "hash": ""
        }
    ]
}'