$.validator.addMethod("allowed_template_variables", function(value, element, param) {
    var variableRegex  = /\{\{(.*?)\}\}/g,
        variables = _.map(value.match(variableRegex), function(x) { return x.replace(/[\{\}]/g, '') }),
        allowedVariables = param.split(',');
    return variables.every(function(x) { return allowedVariables.includes(x) });