docs: function adminAcl(options) {
    var opts = options || {};
  
    if (!opts.secret) {
      throw new Error('missing secret');
    }
  
    var expectedHeader;
    if (opts.prefix) {
      expectedHeader = opts.prefix + ' ' + opts.secret;
    }
    else {
      expectedHeader = module.exports.DEFAULT_PREFIX + opts.secret;
    }
  
    return function (req, res, next) {
      debug('inside of the middleware headerCheck');
  
      var msg401 = { success: false, message: 'Unauthorized' };
  
      if (!req.headers) {
        debug('no headers found - misconfiguration probably');
        return res.status(401).send(msg401);
      }
      
      if (!req.headers.authorization) {
        debug('no authorization header found');
        return res.status(401).send(msg401);
      }
  
      debug('we have a token it seems');
      var receivedHeader = req.headers.authorization;
  
      if (secureCompare(receivedHeader, expectedHeader)) {
        next();
      }
      else {
        debug('failed on secret match');
        return res.status(401).send(msg401);
      }
    };
  }