Come to think of it, `Content-Location` is much more semantically appropriate than `Link <ipfs:hash>; rel="alternate"`; the latter is just a link, but the `Content-Location` header would tell you the canonical location of the requested content. For an IPFS enabled client, this would mean that if they want that specific content, they'd never even hit the HTTP server on subsequent requests, but dive straight into IPFS. That said, existing clients may get very confused by an unsupported scheme in that header. Presumably, that client should go `IDK lol` and go use the not-so-canonical URL instead, but I'd be surprised if they'd actually work like that.