Disable media federation

[catfromplan9]

Your use case

What would you like to do?

Fetch media from server it originates from, not your homeserver

Why would you like to do it?

Use in combination with matrix-org/synapse#15197 to block the media of good servers being maliciously used with burner accounts to federate over illegal content, with this feature server admins will even be able to block all homeservers with the synapse feature and totally prevent file uploads, whilst not compromising on usability

How would you like to achieve it?

Option in preferences tab

Have you considered any alternatives?

Option to require authentication for accessing remote media in upstream matrix spec and synapse. This is not a real fix and only protects private servers from abuse, but it would be nice to have

Additional context

No response