//the export of the entry to the app is as follows:

module.exports = function(schema, options){
...

}


  options.findByUsername = options.findByUsername || function(model, queryParameters) { return model.findOne(queryParameters); }

schema.statics.register = function (user, password, callback) {
  if (!(user instanceof this)) {
        user = new this(user);
      }
      if (!user.get(options.usernameField)) {
        return callback(setMessages(errors.missingUsername, 'error', 406));
      }
    let self = this;
    self.findByUsername(user.get(options.usernameField), true, function(err, existingUser) {
      if (err) { return callback(setMessages(errors.unknown, 'error', 400)); }
      if (existingUser) {
        return callback(setMessages(errors.userExists, 'error', 409));
      }
      user.setPassword(password, (setPasswordErr, user) => {
        if (setPasswordErr) { return callback(setPasswordErr); }
        user.save((saveErr) => {
          if (saveErr) { return callback(saveErr); }
          return callback(null, user, setMessages(success.createdAccount, 'success', 200));
        });
      });
    });
  };

schema.statics.findByUsername = function(username, selectPassword, callback) {
    if (typeof callback === 'undefined') {
      callback = selectPassword;
      selectPassword = false;
    }
    if (username !== undefined) {
      username = username.toLowerCase();
    }
    let queryOrParameters = [];
    for (var i = 0; i < options.usernameQueryFields.length; i++) {
      var parameter = {};
      parameter[options.usernameQueryFields[i]] = username;
      queryOrParameters.push(parameter);
    }
    const query = options.findByUsername(this, { $or: queryOrParameters });
    if (callback) {
      query.exec(callback);
    } else {
      return query;
    }
  };