def rename_projector_message_slides(apps, schema_editor):
    """
    Renames projector message slides in projector model.

    Old name 'core/projectormessage', new name 'core/projector-message'.
    """
    Projector = apps.get_model('core', 'Projector')
    for projector in Projector.objects.all():
        new_config = {}
        for key, value in projector.config.items():
            new_config[key] = value
            if value['name'] == 'core/projectormessage':
                new_config[key]['name'] = 'core/projector-message'
        projector.config = new_config
        projector.save(skip_autoupdate=True)
