S3: expose more properties, possible backward incompatible change

Before these changes we implictly set S3ForcePathStyle if an endpoint
was provided.

This can cause issues with some S3 compatible object storages and must
be explicitly set now.

AWS is also deprecating this setting

https://aws.amazon.com/it/blogs/aws/amazon-s3-path-deprecation-plan-the-rest-of-the-story/

vfs/s3fs.go

@@ -84,16 +84,25 @@ func NewS3Fs(connectionID, localTempDir, mountPath string, config S3FsConfig) (F
 
 	if fs.config.Endpoint != "" {
 		awsConfig.Endpoint = aws.String(fs.config.Endpoint)
+	}
+	if fs.config.ForcePathStyle {
 		awsConfig.S3ForcePathStyle = aws.Bool(true)
 	}
-
 	if fs.config.UploadPartSize == 0 {
 		fs.config.UploadPartSize = s3manager.DefaultUploadPartSize
 	} else {
 		fs.config.UploadPartSize *= 1024 * 1024
 	}
 	if fs.config.UploadConcurrency == 0 {
-		fs.config.UploadConcurrency = 2
+		fs.config.UploadConcurrency = s3manager.DefaultUploadConcurrency
+	}
+	if fs.config.DownloadPartSize == 0 {
+		fs.config.DownloadPartSize = s3manager.DefaultDownloadPartSize
+	} else {
+		fs.config.DownloadPartSize *= 1024 * 1024
+	}
+	if fs.config.DownloadConcurrency == 0 {
+		fs.config.DownloadConcurrency = s3manager.DefaultDownloadConcurrency
 	}
 
 	sessOpts := session.Options{
@@ -201,6 +210,9 @@ func (fs *S3Fs) Open(name string, offset int64) (File, *pipeat.PipeReaderAt, fun
 			Bucket: aws.String(fs.config.Bucket),
 			Key:    aws.String(name),
 			Range:  streamRange,
+		}, func(d *s3manager.Downloader) {
+			d.Concurrency = fs.config.DownloadConcurrency
+			d.PartSize = fs.config.DownloadPartSize
 		})
 		w.CloseWithError(err) //nolint:errcheck
 		fsLog(fs, logger.LevelDebug, "download completed, path: %#v size: %v, err: %v", name, n, err)