title: update model and association in sequelize
body: <p>To have a vague idea, having a model "Account"</p>
  
  <pre><code>const Chars = require('./chars');
  const Account = sequelize.define('account', {
   ...
  }
  Account.hasMany(Chars, { as: 'chars', foreignKey: 'accountId' });
  </code></pre>
  
  <p>table chars is like:</p>
  
  <pre><code>id |charId     |accountId  |ival          |bval
  28 |1          |90         |0             |null
  29 |2          |90         |0             |null
  30 |3          |90         |200           |null
  31 |4          |90         |null          |true
  32 |5          |90         |null          |false
  33 |6          |90         |null          |false
  </code></pre>
  
  <p>so "account" has many "chars" but need them to update at once (if possible)</p>
  
  <p>just need some guidance to made a proper update to the account model and rows for table "chars" (association) using sequelize.</p>
  
  <p>should I use some "foreach" ? maybe a "bulkUpdate" ?</p>