OpenID Connect Logout endpoint

[BatteryLove]

Hi there,

Trying to implement an authentication flow with whmcs using OpenID Connect. 

I have implemented the login functionality and it works well but when i try to logout like this:

var endSession = client.endSessionUrl({
    post_logout_redirect_uri: clientConfig.post_logout_redirect_uri,
    id_token_hint: session.access_token,
    state: generators.state(),
  });

I get this error:

TypeError: end_session_endpoint must be configured on the issuer

... and accessing 

https://whmcs.example.com/oauth/openid-configuration.php

i dont see any `end_session_endpoint`.

Any help on how to logout using OpenID Connect would be appreciated!