feat(fedex): add multi-factor authentication support

Add FedexRegistrationService to enable programmatic FedEx carrier
account registration through 2FA workflow. Includes registerAddress,
requestPin, validatePin, and submitInvoice endpoints. Auto-generates
UUID for name parameter when not provided. Integrates service into
EasyPostClient with comprehensive test coverage.

Author: lanej

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

@@ -0,0 +1,9 @@
+package com.easypost.model;
+
+import lombok.Getter;
+
+@Getter
+public final class FedexRegistration extends EasyPostResource {
+    private String status;
+    private String message;
+}

src/main/java/com/easypost/service/EasyPostClient.java

@@ -26,6 +26,7 @@ public class EasyPostClient {
     public final BillingService billing = new BillingService(this);
     public final CarrierAccountService carrierAccount = new CarrierAccountService(this);
     public final CarrierMetadataService carrierMetadata = new CarrierMetadataService(this);
+    public final FedexRegistrationService fedexRegistration = new FedexRegistrationService(this);
     public final CarrierTypeService carrierType = new CarrierTypeService(this);
     public final ClaimService claim = new ClaimService(this);
     public final CustomerPortalService customerPortal = new CustomerPortalService(this);

src/main/java/com/easypost/service/FedexRegistrationService.java

@@ -0,0 +1,116 @@
+package com.easypost.service;
+
+import com.easypost.exception.EasyPostException;
+import com.easypost.http.Requestor;
+import com.easypost.http.Requestor.RequestMethod;
+import com.easypost.model.FedexRegistration;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+
+public class FedexRegistrationService {
+    private final EasyPostClient client;
+
+    /**
+     * FedexRegistrationService constructor.
+     *
+     * @param client The client object.
+     */
+    FedexRegistrationService(EasyPostClient client) {
+        this.client = client;
+    }
+
+    /**
+     * Register the billing address for a FedEx account.
+     *
+     * @param fedexAccountNumber The FedEx account number.
+     * @param params             Map of parameters for address registration.
+     *                           If params does not contain "name", a UUID will be auto-generated.
+     *                           Optional: "easypost_details" object for additional metadata like
+     *                           "reference" or "description".
+     * @return FedexRegistration object.
+     * @throws EasyPostException when the request fails.
+     */
+    public FedexRegistration registerAddress(final String fedexAccountNumber, final Map<String, Object> params)
+            throws EasyPostException {
+        Map<String, Object> processedParams = ensureNameParameter(params);
+        String endpoint = String.format("fedex_registrations/%s/address", fedexAccountNumber);
+
+        return Requestor.request(RequestMethod.POST, endpoint, processedParams, FedexRegistration.class, client);
+    }
+
+    /**
+     * Request a PIN for FedEx account verification.
+     *
+     * @param fedexAccountNumber The FedEx account number.
+     * @param params             Map of parameters for PIN request.
+     *                           Required: "pin_method" - one of "SMS", "CALL", or "EMAIL".
+     *                           If params does not contain "name", a UUID will be auto-generated.
+     *                           Optional: "easypost_details" object for additional metadata.
+     * @return FedexRegistration object.
+     * @throws EasyPostException when the request fails.
+     */
+    public FedexRegistration requestPin(final String fedexAccountNumber, final Map<String, Object> params)
+            throws EasyPostException {
+        Map<String, Object> processedParams = ensureNameParameter(params);
+        String endpoint = String.format("fedex_registrations/%s/pin", fedexAccountNumber);
+
+        return Requestor.request(RequestMethod.POST, endpoint, processedParams, FedexRegistration.class, client);
+    }
+
+    /**
+     * Validate the PIN entered by the user for FedEx account verification.
+     *
+     * @param fedexAccountNumber The FedEx account number.
+     * @param params             Map of parameters for PIN validation.
+     *                           Required: PIN value provided by the user.
+     *                           If params does not contain "name", a UUID will be auto-generated.
+     *                           Optional: "easypost_details" object for additional metadata.
+     * @return FedexRegistration object.
+     * @throws EasyPostException when the request fails.
+     */
+    public FedexRegistration validatePin(final String fedexAccountNumber, final Map<String, Object> params)
+            throws EasyPostException {
+        Map<String, Object> processedParams = ensureNameParameter(params);
+        String endpoint = String.format("fedex_registrations/%s/pin/validate", fedexAccountNumber);
+
+        return Requestor.request(RequestMethod.POST, endpoint, processedParams, FedexRegistration.class, client);
+    }
+
+    /**
+     * Submit invoice information to complete FedEx account registration.
+     *
+     * @param fedexAccountNumber The FedEx account number.
+     * @param params             Map of parameters for invoice submission.
+     *                           Required: Invoice information.
+     *                           If params does not contain "name", a UUID will be auto-generated.
+     *                           Optional: "easypost_details" object for additional metadata.
+     * @return FedexRegistration object.
+     * @throws EasyPostException when the request fails.
+     */
+    public FedexRegistration submitInvoice(final String fedexAccountNumber, final Map<String, Object> params)
+            throws EasyPostException {
+        Map<String, Object> processedParams = ensureNameParameter(params);
+        String endpoint = String.format("fedex_registrations/%s/invoice", fedexAccountNumber);
+
+        return Requestor.request(RequestMethod.POST, endpoint, processedParams, FedexRegistration.class, client);
+    }
+
+    /**
+     * Ensures the "name" parameter exists in the params map.
+     * If not present, generates a UUID (with hyphens removed) as the name.
+     * This follows the pattern used in the web UI implementation.
+     *
+     * @param params The original parameters map.
+     * @return A new map with the "name" parameter ensured.
+     */
+    private Map<String, Object> ensureNameParameter(final Map<String, Object> params) {
+        Map<String, Object> processedParams = new HashMap<>(params);
+        if (!processedParams.containsKey("name") || processedParams.get("name") == null) {
+            String uuid = UUID.randomUUID().toString().replace("-", "");
+            processedParams.put("name", uuid);
+        }
+        return processedParams;
+    }
+}