Can't change Site lang in Account MFE

[cmltaWt0]

I want to link the issue here since the last comment points to a possible Tutor issue.

The current state is the following:

• I can't see the result of Site lang changing action in the Account MFE immediately
• I can see the result after the page reload
• I can see the CORS info (Response body is not available to scripts (Reason: CORS Preflight Did Not Succeed)
  and 405 Method Not Allowed

[regisb]

When I click "save" the following happens:

1. POST to <LMS>/i18n/setlang/
2. redirect to GET <LMS>/ (no idea why)
3. redirect to GET <LMS>/dashboard (probably because the dashboard is the landing page)
4. redirect to GET <MFE>/learner-dashboard (probably because the LMS is configured to point to the MFE dashboard)
5. for some unknown reason this is considered a CORS request, so make OPTION <MFE>/learner-dashboard
6. CORS request is failing because MFEs are really not supposed to support them.

That thing is a bloody mess. As far as I understand, the issue is with step 2. Why, oh why are we trying to GET /? The CORS issue is a false lead, it's only pointing to a side effect of the actual root cause.