adds cpp methods

src/main/java/io/craftgate/adapter/PaymentAdapter.java

@@ -35,6 +35,17 @@ public PaymentResponse complete3DSPayment(CompleteThreeDSPaymentRequest complete
                 completeThreeDSPaymentRequest, PaymentResponse.class);
     }
 
+    public InitCheckoutPaymentResponse initCheckoutPayment(InitCheckoutPaymentRequest initCheckoutPaymentRequest) {
+        String path = "/payment/v1/checkout-payment/init";
+        return HttpClient.post(requestOptions.getBaseUrl() + path, createHeaders(initCheckoutPaymentRequest, path, requestOptions),
+                initCheckoutPaymentRequest, InitCheckoutPaymentResponse.class);
+    }
+
+    public PaymentResponse retrieveCheckoutPayment(String token) {
+        String path = "/payment/v1/checkout-payment?token=" + token;
+        return HttpClient.get(requestOptions.getBaseUrl() + path, createHeaders(path, requestOptions), PaymentResponse.class);
+    }
+
     public DepositPaymentResponse createDepositPayment(CreateDepositPaymentRequest createDepositPaymentRequest) {
         String path = "/payment/v1/deposits";
         return HttpClient.post(requestOptions.getBaseUrl() + path, createHeaders(createDepositPaymentRequest, path, requestOptions),

src/main/java/io/craftgate/request/InitCheckoutPaymentRequest.java

@@ -0,0 +1,37 @@
+package io.craftgate.request;
+
+import io.craftgate.model.Currency;
+import io.craftgate.model.PaymentGroup;
+import io.craftgate.model.PaymentPhase;
+import io.craftgate.request.dto.PaymentItem;
+import lombok.Builder;
+import lombok.Data;
+import lombok.experimental.SuperBuilder;
+
+import java.math.BigDecimal;
+import java.util.List;
+
+@Data
+@SuperBuilder
+public class InitCheckoutPaymentRequest {
+
+    protected BigDecimal price;
+    protected BigDecimal paidPrice;
+
+    @Builder.Default
+    protected BigDecimal walletPrice = BigDecimal.ZERO;
+
+    protected Currency currency;
+    protected PaymentGroup paymentGroup;
+    protected String conversationId;
+    protected Integer installment;
+    protected String callbackUrl;
+
+    @Builder.Default
+    protected PaymentPhase paymentPhase = PaymentPhase.AUTH;
+
+    protected String cardUserKey;
+
+    protected Long buyerMemberId;
+    protected List<PaymentItem> items;
+}

src/main/java/io/craftgate/response/InitCheckoutPaymentResponse.java

@@ -0,0 +1,12 @@
+package io.craftgate.response;
+
+import lombok.Data;
+import lombok.experimental.SuperBuilder;
+
+@Data
+@SuperBuilder
+public class InitCheckoutPaymentResponse {
+
+    protected String token;
+    protected String pageUrl;
+}

src/test/java/io/craftgate/sample/PaymentSample.java

@@ -488,6 +488,56 @@ void complete_3DS_payment() {
         assertNotNull(response);
     }
 
+    @Test
+    void init_checkout_payment() {
+        List<PaymentItem> items = new ArrayList<>();
+
+        items.add(PaymentItem.builder()
+                .name("item 1")
+                .externalId(UUID.randomUUID().toString())
+                .price(BigDecimal.valueOf(30))
+                .build());
+
+        items.add(PaymentItem.builder()
+                .name("item 2")
+                .externalId(UUID.randomUUID().toString())
+                .price(BigDecimal.valueOf(50))
+                .build());
+
+        items.add(PaymentItem.builder()
+                .name("item 3")
+                .externalId(UUID.randomUUID().toString())
+                .price(BigDecimal.valueOf(20))
+                .build());
+
+        InitCheckoutPaymentRequest request = InitCheckoutPaymentRequest.builder()
+                .price(BigDecimal.valueOf(100))
+                .paidPrice(BigDecimal.valueOf(100))
+                .walletPrice(BigDecimal.ZERO)
+                .installment(1)
+                .currency(Currency.TRY)
+                .conversationId("456d1297-908e-4bd6-a13b-4be31a6e47d5")
+                .paymentGroup(PaymentGroup.LISTING_OR_SUBSCRIPTION)
+                .paymentPhase(PaymentPhase.AUTH)
+                .items(items)
+                .build();
+
+        InitCheckoutPaymentResponse response = craftgate.payment().initCheckoutPayment(request);
+
+        assertNotNull(response);
+        assertNotNull(response.getPageUrl());
+        assertNotNull(response.getToken());
+    }
+
+    @Test
+    void retrieve_checkout_payment() {
+        String token = "456d1297-908e-4bd6-a13b-4be31a6e47d5";
+
+        PaymentResponse response = craftgate.payment().retrieveCheckoutPayment(token);
+
+        assertNotNull(response);
+    }
+
     @Test
     void create_deposit_payment() {
         CreateDepositPaymentRequest request = CreateDepositPaymentRequest.builder()