Wrapping multiple calls to directory.getAccounts into a Promise

stormpath_query.js

  var getAccounts = function(directoryHref, usernames, callback) {
    client.getDirectory(directoryHref, function(err, directory) {
      var accountPromises = _.map(usernames, function(username) {
        return new Promise(function(resolve, reject) {
          var foundAccount;
          directory.getAccounts({username: username, expand: 'customData'},
            function(err, accounts) {
              accounts.each(
                function(account, cb) {
                  account.id = account.username;
                  foundAccount = account ;
                  cb();
                },
                function(err) {
                  resolve(foundAccount);
                }
              );
            }
          );
        });
      });
      Promise.all(accountPromises).then(function(accounts) {
        callback(_.compact(accounts));
      });
    });
  };