simplify attach files

app/main.py

@@ -2,6 +2,7 @@
 from fastapi.responses import Response
 from fastapi.responses import StreamingResponse
 
+from app.util import attach_file
 from libraryapi.pergamum import PergamumDownloader
 
 
@@ -14,7 +15,7 @@ async def get_marc(url: str, id: int) -> StreamingResponse:
     response = StreamingResponse(
         pergamumDownloader.download_iso(url, id), media_type="application/marc"
     )
-    response.headers["Content-Disposition"] = f"attachment; filename={id}.mrc"
+    attach_file(response, id, "mrc")
     return response
 
 
@@ -23,5 +24,5 @@ async def get_marcxml(url: str, id: int) -> Response:
     response = Response(
         pergamumDownloader.download_xml(url, id), media_type="application/xml"
     )
-    response.headers["Content-Disposition"] = f"attachment; filename={id}.xml"
+    attach_file(response, id, "xml")
     return response

app/util.py

@@ -0,0 +1,4 @@
+def attach_file(response, name, extension):
+    response.headers[
+        "Content-Disposition"
+    ] = f"attachment; filename={name}.{extension}"