title: Firestore expressjs: how to get document where specific field exists and update the document
body: <p>So I am using expressjs in the firebase cloud function trying to get a document where a specific field is the same as a  value that I already have,  So here is the  piece of code  :</p>
  <pre><code>const email =data.email (this is coming from stripe webhook ) 
    const document = db
          .collection('ConnectedAccounts')
          .where(`email`, '==', email)
          .get();
        console.log('document', document.data());
  </code></pre>
  <p>after getting this document I want to store a new field to it, I have tried the above code but failed, can anyone help?</p>