models\Assignment.js

/**
 * Assignment.js
 */
module.exports = {
  attributes: {
    users: {
      collection: 'user',
      via: 'assignments',
      dominant: true
    }
  }
};

models\User.js

/**
 * User.js
 */
module.exports = {
  attributes: {
    assignments: {
      collection: 'assignment',
      via: 'users'
    }
  }
};