docs: def localeselector():
      """Default locale selector used in abilian applications."""
      # if a user is logged in, use the locale from the user settings
      user = getattr(g, "user", None)
      if user is not None:
          locale = getattr(user, "locale", None)
          if locale:
              return locale
  
      # Otherwise, try to guess the language from the user accept header the browser
      # transmits.  By default we support en/fr. The best match wins.
      return request.accept_languages.best_match(
          current_app.config["BABEL_ACCEPT_LANGUAGES"]
      )