title: How to Filter firestore collection by multiple ids
body: <p>So in my database schema I have something like this </p>
  
  <pre><code>/collections/users/userId1 { 
     ...,
     id,
     relatedContracts: [id1, id2, id3]
  }
  
  /collections/contracts/contractId {
     ...,
     id,
  }
  </code></pre>
  
  <p>In my firebase security rules I have this </p>
  
  <pre><code>    match /contracts/{contract} {
         function isOwnContract() {
             return request.auth.id == resource.data.creatorId || request.auth.id == recipientId
         }
         allow read, write: if isOwnContract()
       }
  </code></pre>
  
  <p>Now I am very confused on how to filter on the client to get only my related contracts. If the introduction of the security rules I can no longer do my filtering on the client. </p>
  
  <p>I know this exists </p>
  
  <pre><code>firestore.collection(CONTRACTS).where(id, "==", contractId)
  </code></pre>
  
  <p>But how do I do this filtering based on multiple ids </p>