Add invoice

{
    "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
    "purchase": "ca27f506-c3a4-4924-9878-316d53640467",
    "purchase_name": "string",
    "buyer": "720848cf-de0c-4355-87e9-070272f1053c",
    "buyer_display_name": "string",
    "buyer_username": "string",
    "buyer_email": "string",
    "buyer_phone": "string",
    "buyer_address": {
        "locality": "string",
        "country": "string",
        "county": "string",
        "street_address": "string",
        "postal_code": "string"
    },
    "merchant_id": "500924a8-3f5e-4c00-beb8-2efcde988aea",
    "merchant_organization_name": "string",
    "merchant_address": {
        "locality": "string",
        "country": "string",
        "county": "string",
        "street_address": "string",
        "postal_code": "string"
    },
    "tax_identification_number": "string",
    "crypto_amount_received": "string",
    "crypto_amount_requested": "string",
    "crypto_currency_code": "string",
    "crypto_currency_family": "string",
    "fiat_amount_requested": "string",
    "fiat_interest_rate_percentage": "string",
    "fiat_interest_rate_amount_requested": "string",
    "fiat_total_amount_requested": "string",
    "fiat_amount_received": "string",
    "fiat_currency": "string",
    "system_payment_fiat_currency": "string",
    "system_payment_exchange_rate": "string",
    "system_payment_exchanged_fiat_amount": "string",
    "system_payment_fee_amount": "string",
    "invoice_due_date": "2019-08-24",
    "status": "unpaid",
    "type": "purchase-invoice",
    "payment_request": {
        "invoice_id": "f4c4edb8-11e0-4b33-bcc1-482dc59ebb32",
        "deposit_address": "string",
        "price": 0,
        "quantity": 0,
        "expiry_time": "string",
        "crypto_currency_code": "string",
        "crypto_currency_family": "BTC",
        "fiat_currency_code": "string",
        "system_payment_fiat_currency": "string",
        "system_payment_exchange_rate": "string",
        "system_payment_exchanged_fiat_amount": "string",
        "payment_asset_type": "CRYPTO",
        "external_payment_link": "string",
        "external_provider": "aquanow",
        "external_provider_transaction_id": "string",
        "created_at": "2019-08-24T14:15:22Z"
    },
    "payout": "string",
    "is_paid_out": true,
    "created_by": "ee824cad-d7a6-4f48-87dc-e8461a9201c4",
    "created_by_name": "string",
    "amount_refunded": 0,
    "amount_refund_remaining": 0,
    "system_payment_fiat_amount_refunded": 0,
    "system_payment_fiat_amount_refund_remaining": 0,
    "fee_percentage": 0,
    "fee_fiat_amount_requested": 0,
    "fee_fiat_amount_received": 0,
    "updated_at": "2019-08-24T14:15:22Z",
    "created_at": "2019-08-24T14:15:22Z",
    "fee_amount_refunded": 0,
    "system_payment_fee_amount_refunded": 0,
    "external_reference": "string",
    "return_url": "string"
}