title: Why doesn't .add() insert value in the column?
body: <p>I'm trying sails.js <strong>association</strong> using <strong>one way reference</strong> (according to <strong>sails.js in action</strong> book). Now, the value of owner is successfully inserted in <strong>owner</strong> column, but value in <strong>cars</strong> column is not inserted.</p>
  
  <p>When I tried <code>console.log(foundDriver)</code> and <code>console.dir(foundDriver)</code>, it showed following things:</p>
  
  <p><strong>{ id: 1, Name: 'asdf' }</strong></p>
  
  <p><strong>{ cars: [Getter/Setter], id: 1, Name: 'asdf' }</strong></p>
  
  <p>My tables (1: <strong>driver</strong>, 2: <strong>car</strong>):</p>
  
  <p><a href="https://i.stack.imgur.com/gbBqH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gbBqH.png" alt="enter image description here"></a>
  <a href="https://i.stack.imgur.com/1hsy1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1hsy1.png" alt="enter image description here"></a></p>
  
  <p>CODE:</p>
  
  <p>Car.js</p>
  
  <pre><code>module.exports = {
    connection: 'mysqlAdapter',
    tableName: 'car',
    attributes: {
      id: {
        type: 'integer',
        primaryKey: true
      },
      Name: {
        type: 'string'
      },
      Brand: {
        type: 'string'
      },
      Model: {
        type: 'string'
      },
      owner: {
        model: 'driver'
      }
    }
  };
  </code></pre>
  
  <p>Driver.js</p>
  
  <pre><code> module.exports = {
   connection: 'mysqlAdapter',
   tableName: 'driver',
   attributes: {
     id: {
       type: 'integer',
       primaryKey: true
     },
     Name: {
       type: 'string'
     },
     cars: {
       collection: 'car'
     }
   }
  };
  </code></pre>
  
  <p>CarController.js</p>
  
  <pre><code>    module.exports = {
      createCars: function (req, res) {
          Driver.findOne({
              id: 1
          }).exec(function (err, foundDriver) {
              if (err) {
                  console.log("Err1" + foundDriver);
              }
              if (!foundDriver) {
                  console.log("Err2");
              }
              Car.create({
                  Name: "car1",
                  Brand: "brnd",
                  Model: "mdl",
                  owner: foundDriver.id
              }).exec(function (err, createdCar) {
                  if (err) {
                      console.log("Err3");
                  }
                  foundDriver.cars.add(createdCar.id);
                      foundDriver.save(function (err) {
                       if (err) {
                           console.log(foundDriver);
  
                        }
                            return res.json({id: 100});
                      });
              });
          });
      }
      };
  </code></pre>