Feature request: Add support for mocking getIdTokenResult.

[simplecohesion]

Most useful for custom claims, which can be used for role-based access control.

  /// Returns a [IdTokenResult] containing the users JSON Web Token (JWT) and
  /// other metadata.
  ///
  /// If [forceRefresh] is `true`, the token returned will be refreshed regardless
  /// of token expiration.
  Future<IdTokenResult> getIdTokenResult([bool forceRefresh = false]) {
    return _delegate.getIdTokenResult(forceRefresh);
  }