Possibility to download videos which require login

[fknives]

Sometimes the link throws the user to the login page, I should fix that also if I can. I imagine it is something like captcha.

I think the easiest resolution for that is to:

Recognize this state
Show an option to the user for authenticating the downloader app (There is a QR code option which could be used to link directly back to the app)
Store the auth token and use in subsequent requests.
Unknowns:

What token needs to be stored and sent
How to get that token in the first place
What happens if the token expires, does the same webpage shows or it is a separate issue?
How to have a test for this case without exposing my own account? Could I create a test account for this reason with secrets?