2.0: Cannot follow accounts using LRDDMethod_WebFinger

I've been trying to figure out why GNU Social won't talk to Misskey. The link to webfinger in Misskey's host-meta file does not have a rel attribute, so GNU Social ignores it in LRDDMethod_HostMeta. I've filed a bug with Misskey regarding this. LRDDMethod_WebFinger tries to use /.well-known/webfinger directly without looking it up, but this method only supports the acct scheme, whereas LRDDMethod_HostMeta also supports http(s). GNU Social needs to perform discovery on http(s) URIs to be able to follow an account on Misskey (or Mastodon), so when LRDDMethod_HostMeta fails, it ends up giving up.

   WebFinger is neutral regarding the scheme of such a
   URI: it could be an "acct" URI [18], an "http" or "https" URI, a
   "mailto" URI [19], or some other scheme.

RFC 7033

#277 2.0: Cannot follow accounts using LRDDMethod_WebFinger