title: How to populate `identifier` and `providers` in Firebase custom authentication?
body: <p>I'm authenticating my users on my web service and then creating <a href="https://firebase.google.com/docs/auth/admin/create-custom-tokens" rel="noreferrer">Firebase custom token</a> via <a href="https://github.com/firebase/php-jwt" rel="noreferrer">php-jwt</a>:</p>
  
  <pre><code>// Requires: composer require firebase/php-jwt
  use Firebase\JWT\JWT;
  
  // Get your service account's email address and private key from the JSON key file
  $service_account_email = ...;
  $private_key = ...;
  
  function create_custom_token($uid, $is_premium_account) {
    global $service_account_email, $private_key;
  
    $now_seconds = time();
    $payload = array(
      "iss" =&gt; $service_account_email,
      "sub" =&gt; $service_account_email,
      "aud" =&gt; "https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit",
      "iat" =&gt; $now_seconds,
      "exp" =&gt; $now_seconds+(60*60),  // Maximum expiration time is one hour
      "uid" =&gt; $uid,
      "claims" =&gt; array(
        "premium_account" =&gt; $is_premium_account
      )
    );
    return JWT::encode($payload, $private_key, "RS256");
  }
  </code></pre>
  
  <p>But the users that I authenticate this way, don't show the administrator-friendly "Identifier" and "Providers" fields in the "Authentication" panel in the Firebase Console:</p>
  
  <p><a href="https://i.stack.imgur.com/GJcBY.png" rel="noreferrer"><img src="https://i.stack.imgur.com/GJcBY.png" alt="enter image description here"></a></p>
  
  <p>The first two are users that I authenticated via this custom authentication process, and the last one is a user that I authenticated directly via Google.</p>
  
  <p>How can I populate the "Identifier" and the "Providers" fields for users created via custom authentication?</p>