Use any custom WebFinger domain for page metadata

lib/pleroma/web/metadata/utils.ex

@@ -55,7 +55,7 @@ def scrub_html(content), do: content
   def user_name_string(user) do
     "#{user.name} " <>
       if user.local do
-        "(@#{user.nickname}@#{Pleroma.Web.Endpoint.host()})"
+        "(@#{user.nickname}@#{Pleroma.Web.WebFinger.domain()})"
       else
         "(@#{user.nickname})"
       end

lib/pleroma/web/web_finger.ex

@@ -96,7 +96,7 @@ def represent_user(user, "XML") do
     |> XmlBuilder.to_doc()
   end
 
-  defp domain do
+  def domain do
     Pleroma.Config.get([__MODULE__, :domain]) || Pleroma.Web.Endpoint.host()
   end