Add changelog and express bucket integ test

Author: RanVaknin

.changes/next-release/feature-AmazonS3-717127d.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "Amazon S3",
+    "contributor": "",
+    "description": "Added `doesObjectExist` and `doesBucketExist` convenience methods to S3Client and S3AsyncClient"
+}

services/s3/src/it/java/software/amazon/awssdk/services/s3/s3express/S3ExpressExtensionMethodsTest.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.services.s3.s3express;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static software.amazon.awssdk.testutils.service.S3BucketUtils.temporaryBucketName;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import software.amazon.awssdk.core.sync.RequestBody;
+import software.amazon.awssdk.regions.Region;
+import software.amazon.awssdk.services.s3.S3Client;
+
+/**
+ * Verify that doesObjectExist/doesBucketExist extension methods work with S3 Express (directory buckets).
+ */
+class S3ExpressExtensionMethodsTest extends S3ExpressIntegrationTestBase {
+
+    private static final Region TEST_REGION = Region.US_EAST_1;
+    private static final String AZ = "use1-az4";
+    private static final String BUCKET = String.format(
+        temporaryBucketName(S3ExpressExtensionMethodsTest.class) + "--%s--x-s3", AZ);
+    private static final String KEY = "test-key";
+
+    private static S3Client s3;
+
+    @BeforeAll
+    static void setup() {
+        s3 = s3ClientBuilder(TEST_REGION).build();
+        createBucketS3Express(s3, BUCKET, AZ);
+        s3.putObject(r -> r.bucket(BUCKET).key(KEY), RequestBody.fromString("hello"));
+    }
+
+    @AfterAll
+    static void teardown() {
+        deleteBucketAndAllContents(s3, BUCKET);
+        s3.close();
+    }
+
+    @Test
+    void doesObjectExist_existingObject_returnsTrue() {
+        assertThat(s3.doesObjectExist(BUCKET, KEY)).isTrue();
+    }
+
+    @Test
+    void doesObjectExist_nonExistentObject_returnsFalse() {
+        assertThat(s3.doesObjectExist(BUCKET, "fake-key")).isFalse();
+    }
+
+    @Test
+    void doesBucketExist_existingBucket_returnsTrue() {
+        assertThat(s3.doesBucketExist(BUCKET)).isTrue();
+    }
+
+    @Test
+    void doesBucketExist_nonExistentBucket_returnsFalse() {
+        String fakeBucket = String.format(
+            temporaryBucketName("nonexistent") + "--%s--x-s3", AZ);
+        assertThat(s3.doesBucketExist(fakeBucket)).isFalse();
+    }
+}