title: Firebase cloud function is not triggered on user deletion
body: <p>I've created a firebase cloud function to be triggered on user deletion, as mentioned in the firebase documentation:</p>
  
  <pre><code>const admin = require('firebase-admin');
  const functions = require('firebase-functions');
  const firestore = admin.firestore();
  admin.initializeApp();
  
  exports.deleteUserData = functions.auth.user().onDelete((event) =&gt; {
    const uid = event.uid;
    const firestorePromise = clearFirestoreData(uid);
  
    return Promise.all([firestorePromise])
        .then(() =&gt; console.log(`Successfully removed data for user #${uid}.`)
    );
  });
  </code></pre>
  
  <p>After deleting the user from my iOS application, by calling:</p>
  
  <pre><code>user.reauthenticate(with: credential) { result, error in
      if let error = error {
          completion(error)
      } else {
          user.delete { error in
              if let error = error {
                  completion(error)
              } else {
                  completion(nil)
              }
          }
      }
  }
  </code></pre>
  
  <p>In firebase, the user is deleted from "Authentication", but the function is not triggered.</p>
  
  <p>If I delete the user directly from "Authentication" in the firebase console, the function is triggered and deletes the user's data successfully.</p>
  
  <p>I am using:</p>
  
  <pre><code>"firebase-admin": "^8.8.0",
  "firebase-functions": "^3.1.0"
  </code></pre>