/* JSON EXAMPLE
{
    "messageId": "PfNxko2cChY94KsiU9cvUL",
    "eventId": "client.updated",    
    "eventSchemaVersion": 1.0,
    "eventInstanceOriginationDateTime": "2022-03-07T00:37:23Z",
    "eventData": {
        "siteId": 123,
        "saleId": 96,
        "purchasingClientId": "100001049",
        "payments": [
            {
                "paymentId": 103,
                "paymentMethodId": 14,
                "paymentMethodName": "Cash",
                "paymentAmountPaid": 300,
                "paymentLastFour": null,
                "paymentNotes": null
            }
        ],
        "saleDateTime": "2018-05-03T16:52:23Z",
        "soldById": 10,
        "soldByName": "Jane Doe",
        "locationId": 1,
        "totalAmountPaid": 150,
        "items": [
            {
                "itemId": 78,
                "type": "Service",
                "name": "10 Punch Pass",
                "amountPaid": 150,
                "amountDiscounted": 0,
                "quantity": 1,
                "recipientClientId": "100000009",
                "paymentReferenceId": 44
            },
            {
                "itemId": 79,
                "type": "Service",
                "name": "10 Kick Pass",
                "amountPaid": 150,
                "amountDiscounted": 0,
                "quantity": 1,
                "recipientClientId": "100000009",
                "paymentReferenceId": 44
            }
        ]
    }
}*/


public class Sale {
public String messageId;
public String eventId;
public Decimal eventSchemaVersion;
public String eventInstanceOriginationDateTime;
public SaleEventData eventData;
}


public class SaleEventData {
public Integer siteId;
public Integer saleId;
public String purchasingClientId;
public List<PaymentDetails> payments;
public String saleDateTime;
public String soldById;
public String soldByName;
public Integer locationId;
public Integer totalAmountPaid;
public List<SaleItemDetails> items;
}

public class PaymentDetails {
public Integer paymentId;
public Integer paymentMethodId;
public String paymentMethodName;
public String paymentAmountPaid;
public Integer paymentLastFour;
public String paymentNotes;
}

public class SaleItemDetails {
public Integer itemId;
public String type;
public String name;
public Integer amountPaid;
public Integer amountDiscounted;
public Integer quantity;
public String recipientClientId;
public Integer paymentReferenceId;
}

Sale mbSale = (Sale)JSON.deserialize(jsonInput, Sale.class);