Use correct domain for fqn and InstanceView

Signed-off-by: marcin mikołajczak <git@mkljczk.pl>

lib/pleroma/user.ex

@@ -2252,7 +2252,7 @@ def full_nickname(%User{} = user) do
     if String.contains?(user.nickname, "@") do
       user.nickname
     else
-      %{host: host} = URI.parse(user.ap_id)
+      host = Pleroma.Web.WebFinger.domain()
       user.nickname <> "@" <> host
     end
   end

lib/pleroma/web/mastodon_api/views/instance_view.ex

@@ -14,7 +14,7 @@ def render("show.json", _) do
     instance = Config.get(:instance)
 
     %{
-      uri: Pleroma.Web.Endpoint.url(),
+      uri: Pleroma.Web.WebFinger.domain(),
       title: Keyword.get(instance, :name),
       description: Keyword.get(instance, :description),
       short_description: Keyword.get(instance, :short_description),

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