title: Firebase token error, "The custom token corresponds to a different audience."
body: <p>I'm trying to generate JWT token for Firebase using Ruby on the server. Before 3.0 we used <a href="https://github.com/firebase/firebase-token-generator-ruby">token generator</a> but it stopped working after the upgrade. The token I get with code below gives an error:</p>
  
  <blockquote>
    <p>The custom token corresponds to a different audience.</p>
  </blockquote>
  
  <p>and I can't find anywhere what it means.</p>
  
  <pre><code>private_key = OpenSSL::PKey::RSA.new &lt;&lt;-PEM
  -----BEGIN PRIVATE KEY-----
  ..redacted..
  -----END PRIVATE KEY-----
  PEM
  
  service_account_email = 'redacted@redacted.iam.gserviceaccount.com'
  now_seconds = Time.now.to_i
  
  payload = {
    iss: service_account_email,
    sub: service_account_email,
    aud: 'https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit',
    iat: now_seconds,
    exp: now_seconds + (60 * 60),
    uid: self.id.to_s,
    debug: true,
    claims: {
      userId: self.id,
      slug: self.slug,
      username: self.username,
      avatar: self.profile.avatar.url,
      group: self.group,
      debug: true
    }
  }
  
  JWT.encode payload, private_key, 'RS256'
  </code></pre>
  
  <p>Thanks</p>