When provided, this setting appends tpa_hint=<value> to the `next` URL provided for /login and /register page URLs, which bypasses the Open edX Login/Register page with an an automatic redirection to the TPA login/register URL.
This allows the already implemented tpa_hint feature to be automatically added to login, registration, and enrolment URLs generated throughout the platform.
Avoids auto-appending the tpa_hint parameter when the request is already in the TPA pipeline, to prevent infinite redirect loops, and adds tests to verify this behaviour.
