REST Server for Users using Restify and Mongoose

I am creating a REST API to access a database of users. I am new to Node.js and developing REST APIs in general. I am also trying to use best security practices.

main.js

var fs = require('fs');
var restify = require('restify');
var bodyParser = require('body-parser');
var mongoose = require('mongoose');
var bcrypt = require('bcrypt');

mongoose.connect('localhost', 'nodejs-sample');

var User = require('./models/user')

// SSL options
var options = {
  certificate: fs.readFileSync('./ssl/cert.pem'),
  key: fs.readFileSync('./ssl/key.pem')
}

var server = restify.createServer(options);

server.use(bodyParser.urlencoded({extended: true}));
server.use(bodyParser.json());

server.get('/users', function(req, res) {
  User.find(function(err, users) {
    if (err) {
      res.send(err);
    }

    res.json(users);
  });
});

server.post('/users', function(req, res) {
  bcrypt.hash(req.body.password, 10, function(err, hash) {
    if (err) {
      res.send(err);
    }

    User.create({
      username: req.body.username,
      first_name: req.body.first_name,
      last_name: req.body.last_name,
      email: req.body.email,
      hash: hash
    }, function(err) {
      if (err) {
        res.send(err)
      }

      res.json({message: 'User added'});
    });
  });
});

server.get('/users/:user_id', function(req, res) {
  User.findById(req.params.user_id, function(err, user) {
    if (err) {
      res.send(err);
    }

    res.json(user);
  });
});

server.put('/users/:user_id', function(req, res) {
  var body = req.body;
  if (body.password) {
    bcrypt.hash(body.password, 10, function(err, hash) {
      if (err) {
        res.send(err);
      }

      delete body.password;
      body.hash = hash;
      User.update({_id: req.params.user_id}, body, function() {
        res.json({message: 'User updated'});
      });
    });
  } else {
    User.update({_id: req.params.user_id}, body, function() {
      res.json({message: 'User updated'});
    });
  }
});

server.del('/users/:user_id', function(req, res) {
  User.findByIdAndRemove(req.params.user_id, function(err) {
    if (err) {
      res.send(err);
    }

    res.json({message: 'User deleted'});
  });
});

server.listen(process.env.PORT || 8080, function() {
  console.log('%s listening at %s', server.name, server.url);
});

models/user.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var UserSchema = new Schema({
  username: {
    type: String,
    required: true,
    unique: true
  },
  first_name: {
    type: String,
    required: true
  },
  last_name: {
    type: String,
    required: true
  },
  email: {
    type: String,
    required: true
  },
  hash: {
    type: String,
    required: true
  }
});

// remove hash from JSON output
UserSchema.methods.toJSON = function() {
  var obj = this.toObject();
  delete obj.hash;
  return obj;
};

UserSchema.methods.verifyPassword = function(password, cb) {
  bcrypt.compare(password, this.hash, function(err, res) {
    if (err) {
      return cb(err);
    }

    cb(null, res);
  });
};

module.exports = mongoose.model('User', UserSchema);