title: Is it possible to force a foreign key to exist using Sequelize?
body: <p>My model is:</p>
  
  <pre><code>module.exports = function(sequelize, DataTypes) {
    return Person = sequelize.define('Person', {
      PersonTime: {
        type: DataTypes.INTEGER,
        allowNull: false
      },
      message: {
        type: DataTypes.STRING,
        allowNull: false
      }
    }, {
      classMethods: {
        associate: function(models) {
          return Person.hasMany(models.Thought, {
            foreignKey: 'PersonId'
          });
        }
      }
    });
  };
  </code></pre>
  
  <p>I want to force every Person to belong to a Thought and therefore in the <code>Thought</code> table, I want the <code>PersonId</code> field to be required. How can I do this?</p>