Fix #2706 - Always respond with 200 to PuSH payloads (#2733)

Fix #2196 - Respond with 201 when Salmon accepted, 400 when unverified
Fix #2629 - Correctly handle confirm_domain? for local accounts
Unify rules for extracting author acct from XML, prefer <email>, fall back
to <name> + <uri> (see also #2017, #2172)

app/services/fetch_remote_account_service.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class FetchRemoteAccountService < BaseService
+  include AuthorExtractor
+
   def call(url, prefetched_body = nil)
     if prefetched_body.nil?
       atom_url, body = FetchAtomService.new.call(url)
@@ -19,21 +21,10 @@ class FetchRemoteAccountService < BaseService
     xml = Nokogiri::XML(body)
     xml.encoding = 'utf-8'
 
-    email = xml.at_xpath('//xmlns:author/xmlns:email').try(:content)
-    if email.nil?
-      url_parts = Addressable::URI.parse(url).normalize
-      username  = xml.at_xpath('//xmlns:author/xmlns:name').try(:content)
-      domain    = url_parts.host
-    else
-      username, domain = email.split('@')
-    end
+    account = author_from_xml(xml.at_xpath('/xmlns:feed', xmlns: TagManager::XMLNS))
 
-    return nil if username.nil? || domain.nil?
-
-    Rails.logger.debug "Going to webfinger #{username}@#{domain}"
-
-    account = FollowRemoteAccountService.new.call("#{username}@#{domain}")
     UpdateRemoteProfileService.new.call(xml, account) unless account.nil?
+
     account
   rescue TypeError
     Rails.logger.debug "Unparseable URL given: #{url}"