webp thumbnail support with png fallback

src/documents/views.py

@@ -362,7 +362,12 @@ class DocumentViewSet(
                 handle = doc.thumbnail_file
             # TODO: Send ETag information and use that to send new thumbnails
             #  if available
-            return HttpResponse(handle, content_type="image/png")
+            content_type = (
+                "image/webp"
+                if os.path.splitext(doc.thumbnail_path)[1] == ".webp"
+                else "image/png"
+            )
+            return HttpResponse(handle, content_type=content_type)
         except (FileNotFoundError, Document.DoesNotExist):
             raise Http404()