Add support for Frontier MSO.

[CplPwnies]

Checklist

• I'm reporting a feature request
• I've verified that I'm running youtube-dl version 2020.03.08
• I've searched the bugtracker for similar feature requests including closed ones

Description

PS C:\src-youtube-dl-2020.03.08> python -m youtube_dl --version
2020.03.08

First off, I know this is a duplicate of #11867, but that thread is locked and I wanted to add some additional information and findings.

It seems that the MVPD name is now frontier_auth-gateway_net

Additionally, there are several redirects that need to be followed in order to get to the login page, but youtube-dl seems to stop at the initial adobe redirect page, mainly because there is no post url to extract. There is some javascript on the page that does the auto-redirect using

There is an authstate token that gets passed all the way through to the login page, and I've been working in the source to grab that out, but I can't get it to either follow the redirect all the way through or use the authstate token (pulled from the webpage) to formulate a better URL. I need someone with better understanding of the code base to help. I can also provide credentials for testing.