fix: ensure start message sent before body

Author: alukach

src/stac_auth_proxy/utils/middleware.py

@@ -58,23 +58,25 @@ async def transform_response(message: Message) -> None:
                 # Delay sending start message until we've processed the body
                 start_message = message
                 return
+
             assert start_message is not None
+
+            headers = MutableHeaders(scope=start_message)
+
             if not self.should_transform_response(
                 request=Request(scope),
-                response_headers=Headers(scope=start_message),
+                response_headers=headers,
             ):
-                return await send(message)
-            if message["type"] != "http.response.body":
-                return await send(message)
+                await send(start_message)
+                await send(message)
+                return
 
             body += message["body"]
 
             # Skip body chunks until all chunks have been received
             if message.get("more_body"):
                 return
 
-            headers = MutableHeaders(scope=start_message)
-
             # Transform the JSON body
             if body:
                 data = json.loads(body)