Added support for DynamoDbAutoGeneratedKey annotation

Author: anasatirbasa

services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/functionaltests/AutoGeneratedKeyRecordTest.java

@@ -261,6 +261,7 @@ public void autogenerateKey_setOnInvalidKeyAttribute_throws_exception() {
 
     @Test
     public void autogenerateKey_onVersionedRecord_setOnPrimaryKey_performsUuidGeneration() {
+        // NOTE: UpdateBehavior has no effect on primary keys since they cannot be null in DynamoDB
         DynamoDbEnhancedClient client = DynamoDbEnhancedClient.builder()
                                                               .dynamoDbClient(getDynamoDbClient())
                                                               .extensions(AutoGeneratedKeyExtension.builder().build(),
@@ -582,6 +583,7 @@ public static class VersionedRecord {
         private Long version;
         private String payload;
 
+        // NOTE: UpdateBehavior has no effect on primary keys since they cannot be null in DynamoDB
         @DynamoDbPartitionKey
         @DynamoDbAutoGeneratedKey
         public String getId() {
@@ -650,7 +652,6 @@ public void setId(String id) {
         // since primary keys cannot be null in DynamoDB and are required for UpdateItem
         @DynamoDbSortKey
         @DynamoDbAutoGeneratedKey
-        @DynamoDbUpdateBehavior(UpdateBehavior.WRITE_IF_NOT_EXISTS)
         public String getSortKey() {
             return sortKey;
         }