Improve messaging when app url returns 3xx

[pavelloz]

Turns out redirect cuts off auth headers ( mdyd-dev/desksnearme#8605 (comment) ), so new plan:

• Inform user whats going on
• Propose correct url (the one that redirect points to)

1. Create instance
2. Add 2 domains
3. Redirect a domain to second
4. Add the redirected domain to pos-cli
5. There is no info about why is it not working