style: use lowercase headers

Author: dreinon

storage3/_async/file_api.py

@@ -172,7 +172,7 @@ async def upload(
             file_options = {}
         headers = {**self._client.headers, **DEFAULT_FILE_OPTIONS, **file_options}
         filename = path.rsplit("/", maxsplit=1)[-1]
-        files = {"file": (filename, open(file, "rb"), headers.pop("contentType"))}
+        files = {"file": (filename, open(file, "rb"), headers.pop("content-type"))}
         _path = self._get_final_path(path)
 
         return await self._request(

storage3/constants.py

@@ -7,7 +7,7 @@
     },
 }
 DEFAULT_FILE_OPTIONS = {
-    "cacheControl": "3600",
-    "contentType": "text/plain;charset=UTF-8",
+    "cache-control": "3600",
+    "content-type": "text/plain;charset=UTF-8",
     "x-upsert": "false",
 }