fix(internal): make toFile use input file's options (#727)

Author: stainless-bot

Diff for: src/uploads.ts

@@ -102,11 +102,14 @@ export type ToFileInput = Uploadable | Exclude<BlobLikePart, string> | AsyncIter
 export async function toFile(
   value: ToFileInput | PromiseLike<ToFileInput>,
   name?: string | null | undefined,
-  options: FilePropertyBag | undefined = {},
+  options?: FilePropertyBag | undefined,
 ): Promise<FileLike> {
   // If it's a promise, resolve it.
   value = await value;
 
+  // Use the file's options if there isn't one provided
+  options ??= isFileLike(value) ? { lastModified: value.lastModified, type: value.type } : {};
+
   if (isResponseLike(value)) {
     const blob = await value.blob();
     name ||= new URL(value.url).pathname.split(/[\\/]/).pop() ?? 'unknown_file';