Update DirecTV Now to AT&T TV

[ryaniskira]

Checklist

• I'm reporting a feature request
• I've verified that I'm running youtube-dl version 2020.07.28
• I've searched the bugtracker for similar feature requests including closed ones

Description

I can not download anything from Discovery Go or any related networks by passing my AT&T TV (--ap-list-mso: ATTOTT) login credentials. It seems that the rebrand of Direct TV Now to AT&T TV might be interfering with Youtube-dl's ability to use the login credentials. I know it's not a geo blocking issue because I can login and watch content via my browser without issue, here's proof, as well as the actual link to demonstrate it's not one of the free episodes that doesn't require a login, and passing a cookie file to Youtube-dl does work. On top of it these exact same credentials worked before the rebrand to AT&T TV. Here is the current code concerning ATTOTT:

    'ATTOTT': {
        'name': 'DIRECTV NOW',
        'username_field': 'email',
        'password_field': 'loginpassword',
    },

But when presented with the AT&T TV Login page (when logging in via the browser) the username field ID is userName while the password field ID is password as shown here so I forked Youtube-dl to change that to the field ID:

    'ATTOTT': {
        'name': 'AT&T TV',
        'username_field': 'userName',
        'password_field': 'password',
    },

and when that didn't work I tried the field name (both with and without the underscore in USER ID):

    'ATTOTT': {
        'name': 'AT&T TV',
        'username_field': 'User_ID',
        'password_field': 'Password',
    },

but neither seem to get AT&T TV/DirecTV now back up and running. I do have an active login so I can help troubleshoot this as much as needed to get this login in working order again. I am not being geo-restricted: I am a US Citizen, I am currently physically in the US, using a US TV provider (AT&T TV), attempting to use a US service.