title: firestore query filter based on a collection
body: <p>I have a <code>book</code> collection in firestore, by design each document has an <code>id</code> (say it's integer ids like 0, 1, 2..); I want to query the collection by filtering a <em>random</em> collection of document <code>id</code> e.g. [2, 5, 23, 54], note that these ids are random so I can't use range filter like <code>isGreaterThan</code>.
  I want to avoid querying once for each filtered id as it may read the database too many times (which can be costly).</p>
  
  <p>I tried to use <code>Firestore.instance.collection('book')where('id', array_contains:[ filtered id])</code> but this doesn't work since <code>id</code> isn't a collection field.</p>