The functions has_relay/get_relay are not respecting custom application actors as retrieved by nodeinfo.

The pull requests !1509 (merged) and !1507 (merged) introduced fetching a custom "relay"/application-actor via nodeinfo. But when following an instance via it's application actor that way the follow is not correctly displayed in the admin menu, because the function has_relay needs to return true for this application actor. has_relay uses get_relay which only checks for hardcoded applications actors for Mastodon and Mobilizon.