Link preview localization #1279
Description
Summary
Follow-up to #1243
Turns out Telegram, Signal & probably others request link previews with Accept-Language: en-US even when the requesting app is set to Spanish.
This means link previews currently always display in English.
Proposed fix
Add an &l=es, etc to the end of generated links. This is still imperfect: the link preview will show the language of whoever generated the link, not whoever is about to click the link. But I think it's the best we can do given the messaging apps' behavior.
Apps probably request previews this way so that they can cache a single preview per URL, rather than one per (URL, viewer langage).