old_contents: from django.apps import AppConfig
  from django.utils.translation import gettext_lazy as _
  
  
  class TrekkingConfig(AppConfig):
      name = 'geotrek.trekking'
      verbose_name = _("Trekking")
  
new_contents: from django.apps import AppConfig
  from django.core.checks import register, Tags
  from django.utils.translation import gettext_lazy as _
  
  
  class TrekkingConfig(AppConfig):
      name = 'geotrek.trekking'
      verbose_name = _("Trekking")
  
      def ready(self):
          from .forms import TrekForm
  
          def check_hidden_fields_settings(app_configs, **kwargs):
              # Check all Forms hidden fields settings
              errors = TrekForm.check_fields_to_hide()
              return errors
  
          register(check_hidden_fields_settings, Tags.security)
  
subject: Add system checks for Trek form