Implement Deezer OAuth user authentication and request specific permission scopes such as manage_library and offline_access

Steps

1. Register an application on Deezer for Developers to get an app_id and app secret
2. Redirect the user to Deezer's OAuth authorize URL with your app_id, redirect_uri, and a `perms` parameter listing the comma-separated permissions you need (e.g. basic_access, email, manage_library, offline_access)
3. Handle the redirect callback containing an authorization code, then exchange it for an access token via Deezer's token endpoint using your app_id and secret
4. Request `offline_access` explicitly if you need a token that does not expire, since the default token has a limited lifetime
5. Store the access token and use it as a query parameter or bearer credential on subsequent Deezer API calls that touch user data
6. Re-request authorization (with the updated `perms` list) if you later need additional scopes, since Deezer scopes are granted at authorization time, not incrementally