Properly re-map og: tags

server.py

@@ -241,6 +241,10 @@ def preview_url(
                 logging.exception("Failed to fetch url for OG tags @ %r: %r", _url, e, exc_info=True)
                 og_tags.pop(tag_name, None)
 
+    for key in og_tags.copy().keys():
+        if not key.startswith(("original:", "og:", "matrix:")):
+            value = og_tags.pop(key, None)
+            og_tags["og:" + key] = value
     return og_tags