feat: adds surcharges property and model to Rate object

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Next Release
 
+- Adds `surcharges` property and model to `Rate` object
 - Removes the deprecated, unusable `addCreditCardToUser` function
   - Stripe has disabled the ability to pass plain credit card details over the wire and now requires using [Stripe.js/Elements/Checkout](https://support.stripe.com/questions/card-tokenization-restrictions-using-publishable-keys). Follow the [Decentralized (EasyPost-Manage Billing) Guide](https://docs.easypost.com/guides/get-started-with-forge/easypost-managed-billing-guide#referralcustomer-billing-management) for more details on the new flow to use.
   - Makes `referralCustomer.retrieveEasypostStripeApiKey` public to help facilitate adding credit cards using Stripe.js

src/main/java/com/easypost/model/Rate.java

@@ -1,5 +1,6 @@
 package com.easypost.model;
 
+import java.util.List;
 import java.util.Map;
 
 import lombok.Getter;
@@ -22,4 +23,5 @@ public class Rate extends EasyPostResource {
     private String carrierAccountId;
     private String billingType;
     private Map<String, String> details;
+    private List<Surcharge> surcharges;
 }

src/main/java/com/easypost/model/Surcharge.java

@@ -0,0 +1,14 @@
+package com.easypost.model;
+
+import lombok.Getter;
+
+@Getter
+public final class Surcharge {
+    private String object;
+    private String type;
+    private String category;
+    private String amount;
+    private String listAmount;
+    private String retailAmount;
+    private String currency;
+}