add configuration for MPU threshold for CRT

generated/src/aws-cpp-sdk-s3-crt/include/aws/s3-crt/S3CrtClientConfiguration.h

@@ -143,6 +143,16 @@ namespace Aws
                     uint32_t maxBackoffSecs = 20;
                 } config;
             } crtRetryStrategyConfig;
+
+            /**
+             * Optional.
+             * The size threshold in bytes for when to use multipart uploads.
+             * Uploads larger than this will use the multipart upload strategy.
+             * Uploads smaller or equal to this will use a single HTTP request.
+             * If set, this should be at least `partSize`.
+             * If not set, the max of `partSize` and 5 MiB will be used.
+             */
+            Crt::Optional<size_t> multipartUploadThreshold{};
             /* End of S3 CRT specifics */
         private:
             void LoadS3CrtSpecificConfig(const Aws::String& profileName);

generated/src/aws-cpp-sdk-s3-crt/source/S3CrtClient.cpp

@@ -381,6 +381,10 @@ void S3CrtClient::init(const S3Crt::ClientConfiguration& config,
 
   static const size_t DEFAULT_PART_SIZE = 8 * 1024 * 1024; // 8MB
   s3CrtConfig.part_size = config.partSize < DEFAULT_PART_SIZE ? DEFAULT_PART_SIZE : config.partSize;
+  static const uint64_t FIVE_MB = 5 * 1024 * 1024;
+  s3CrtConfig.multipart_upload_threshold = config.multipartUploadThreshold.has_value() ?
+    config.multipartUploadThreshold.value() :
+    std::max(s3CrtConfig.part_size, FIVE_MB);
 
   Aws::Crt::Io::TlsConnectionOptions *rawPTlsConnectionOptions = nullptr;
   if (config.tlsConnectionOptions)

tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/s3/s3-crt/S3CrtClientConfigHeader.vm

@@ -76,4 +76,14 @@
                     uint32_t maxBackoffSecs = 20;
                 } config;
             } crtRetryStrategyConfig;
+
+            /**
+             * Optional.
+             * The size threshold in bytes for when to use multipart uploads.
+             * Uploads larger than this will use the multipart upload strategy.
+             * Uploads smaller or equal to this will use a single HTTP request.
+             * If set, this should be at least `partSize`.
+             * If not set, the max of `partSize` and 5 MiB will be used.
+             */
+            Crt::Optional<size_t> multipartUploadThreshold{};
             /* End of S3 CRT specifics */

tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/s3/s3-crt/S3CrtServiceClientSourceInit.vm

@@ -408,6 +408,10 @@ void ${className}::init(const ${clientConfigurationNamespace}::ClientConfigurati
 
   static const size_t DEFAULT_PART_SIZE = 8 * 1024 * 1024; // 8MB
   s3CrtConfig.part_size = config.partSize < DEFAULT_PART_SIZE ? DEFAULT_PART_SIZE : config.partSize;
+  static const uint64_t FIVE_MB = 5 * 1024 * 1024;
+  s3CrtConfig.multipart_upload_threshold = config.multipartUploadThreshold.has_value() ?
+    config.multipartUploadThreshold.value() :
+    std::max(s3CrtConfig.part_size, FIVE_MB);
 
   Aws::Crt::Io::TlsConnectionOptions *rawPTlsConnectionOptions = nullptr;
   if (config.tlsConnectionOptions)