WIP: MSC3911: Handle media that are attached to redacted media - via quarantine

[itsoyou]

Linked Media MSC3911 AP?: Media deletion on redaction #3366

This is another way of handling attached media when the event is redacted, using quarantine.
Deletion can be handled by retention rule with delete_quarantined_media enabled option

• [] When an event is redacted, media attached to it should also be deleted.
• [] When the content of an event would be redacted (because of a redaction), the attached media should also be deleted. This should apply to local and remote media.
• [] We may need to support a delay for moderators, in which case downloads should be immediately restricted for normal users and still be available for moderators, then the media deleted later.

Questions

• what endpoint will moderators use to access to the media that are attached to the redacted events?
• At the moment quarantining a media also quarantines its hash. This might cause unexpected problem.
• maybe we can introduce the option to only redact the media not its hash

The quarantined media will be deleted automatically