'Change a multi\'s markdown description.'

@require_oauth2_scope('read')
@validate(VUser(), VModhash(), multi=VMultiByPath('multipath', require_edit=True, kinds='m'), data=VValidatedJSON('model', multi_description_json_spec))
@api_doc(api_section.multis, extends=GET_multi_description)
def PUT_multi_description(self, multi, data):

    multi.description_md = data['body_md']
    multi._commit()
    return self._format_multi_description(multi)
