When linking to the Matrix Public Archive, make sure URL previews look good

[MadLittleMods]

If someone links to the Matrix Public Archive, we should make sure the URL previews look good.

When linking the homepage, a sensible description and image

When linking to a specific event, the URL preview should show the event contents:

.../r/foo.bar/date/2022/11/01?at=$abcd

When linking to a room on a given day, TODO

.../r/foo.bar/date/2022/11/01

When linking to a room, TODO

.../r/foo.bar

Dev notes

Synapse URL preview:

• synapse/media/url_previewer.py

References:

• GET /_matrix/media/v3/preview_url: https://spec.matrix.org/v1.6/client-server-api/#get_matrixmediav3preview_url
  • Synapse uses https://ogp.me/
• https://medium.com/slack-developer-blog/everything-you-ever-wanted-to-know-about-unfurling-but-were-afraid-to-ask-or-how-to-make-your-e64b4bb9254

URL preview debuggers:

• https://cards-dev.twitter.com/validator
• https://developers.facebook.com/tools/debug/

[MadLittleMods]

@clokep Any tips for what we need to add to the page (<meta>)? What drives the URL preview in Element (title, description, image)?

Pinging you because I recall you caring about them and poking around whenever you see a bad one.