sequelize one to many
// To create a One-To-Many relationship in Sequelize,
// the `hasMany` and `belongsTo` associations are used together:
const City = sequelize.define('city', {...});
const Country = sequelize.define('country', {...});
Country.hasMany(City);
City.belongsTo(Country);
// Read more: https://sequelize.org/v4/manual/tutorial/associations.html#one-to-many-associations-hasmany-