@Gwenole_Midy Instead of overriding whole user permissions just to add scope for SSO auth.
I used a different approach for it which found out to be a easy solution.
I copied the purest SSO code into my src\extensions\users-permissions\strapi-server.js and added the scopes I wanted from Facebook but please note there isn’t any way to add scopes for google.
I hope this will help someone 
.