fix aka parsing

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -1531,6 +1531,10 @@ defp normalize_image(%{"url" => url}) do
   defp normalize_image(urls) when is_list(urls), do: urls |> List.first() |> normalize_image()
   defp normalize_image(_), do: nil
 
+  defp normalize_also_known_as(aka) when is_list(aka), do: aka
+  defp normalize_also_known_as(aka) when is_binary(aka), do: [aka]
+  defp normalize_also_known_as(nil), do: []
+
   defp object_to_user_data(data, additional) do
     fields =
       data
@@ -1576,6 +1580,7 @@ defp object_to_user_data(data, additional) do
     also_known_as =
       data
       |> Map.get("alsoKnownAs", [])
+      |> normalize_also_known_as()
       |> Enum.filter(fn url ->
         case URI.parse(url) do
           %URI{scheme: "http"} -> true

lib/pleroma/web/o_auth/o_auth_controller.ex

@@ -558,10 +558,9 @@ def register(%Plug.Conn{} = conn, %{"authorization" => _, "op" => "register"} =
     else
       {:error, changeset} ->
         message =
-          Enum.map(changeset.errors, fn {field, {error, _}} ->
+          Enum.map_join(changeset.errors, "; ", fn {field, {error, _}} ->
             "#{field} #{error}"
           end)
-          |> Enum.join("; ")
 
         message =
           String.replace(