URL preview #301
Description
Implement links preview for links placed in their own line. Use open-graph (og). Generating the content server side would require a task and re-parsing the raw comment. Check it was not modified in the meantime, and atomically update it using the timestamp. We could use JS instead but making requests to random sites without the user consent doesn't sound good.
On a second thought we already do random requests to get images, so fetching the og content would not be worse than that. I'm more incline in solving this with JS.