How to add email claim using oidc_user_claims ?

Hey folks!

I'm trying to use this in conjection with https://github.com/mesosphere/traefik-forward-auth - I need an email claim to validate, so I tried the following client setup:

```
add_filter( 'oidc_registered_clients', 'my_oidc_clients' );
function my_oidc_clients() {
return array(
'clientid' => array(
'name' => 'My Awesome Name',
'secret' => 'clientsecret',
'grant_types' => array( 'authorization_code' ),
'scope' => 'openid profile email'
),
);
}
```

And then I added:

```
add_filter( 'oidc_user_claims', 'my_user_claims', 10, 2 );
function my_user_claims($claims, $user) {
$claims['email'] = $user->user_email;
return $claims;
}
```

Hoping to get the email address returned. However, my claim (when debugged with https://openidconnect.net/), doesn't show the email field.

Have I misunderstood how to achieve this? :)

Thanks!
D

Start by tracing the oidc_user_claims filter and the oidc_registered_clients configuration in the plugin, then reproduce the authorization-code flow with the shown client and email scope. Confirm whether the returned claims include email when inspected with openidconnect.net; document the required configuration or identify the failing path.

Written by the indexing model from the issue text.