Reads a user's language from the actor.

Name one in the domain's gettext block with locale_resolver. It is called only with a non-nil actor. Return nil to use Gettext's current process language.

defmodule MyApp.LocaleResolver do
  @behaviour AshGettext.Locale.Resolver

  @impl true
  def resolve(%{language: language}), do: language
  def resolve(_actor), do: nil
end