How does this work? How do you host pixelfed.domain.com and mastodon.domain.com together in the same domain, with queries for “@[email protected]” to the webfinger host path?
I’m other words, how does the querying application know which resource it needs? How do you know that a pixelfed instance will get the pixelfed resource versus the mastodon resource?
I think what they mean is a service to provide the webfinger response in a customizable manner. I know for me right now, I’m just using wildcards in nginx to handle it for the ActivityPub path, but it’s not really ideal because it won’t work for other activitypub services as far as I can tell.