Adds employee ID to user data

[helmo-nico]

The issue was this:

1. In Moodle, configure:

• "auth_oidc | field_map_idnumber" to "employeeId"
• "auth_oidc | field_updatelocal_idnumber" to "always"

2. In Entra ID, bind the employeeId so it's returned in the token.

3. During authentication, the get_userinfo($username) function retrieves the token and extracts several pieces of information, but not the employeeId.

4. The apply_configured_fieldmap_from_token(array $userdata, string $eventtype) function receives these partial user data, and since employeeId is missing from $userdata, it cannot be updated.

My patch does the following:

Map employee_id from token claims when not set. Enables binding employee_id to user data based on auth_oidc_field_mapping configuration.

By adding employeeId handling to the get_userinfo($username) function, the idnumber field now updates correctly during user login, in accordance with the administrator's configuration.