[twitch] Switch access token to GraphQL and refactor.

[23rd]

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• Bug fix
• Improvement
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---

Description of your pull request and other information

The main purpose of this PR is switching endpoint for the access token from the old api.twitch.tv/api to the newest GraphQL.
Looks like the api.twitch.tv/api endpoint is still working, but it will be rejected at any time. The twitch.tv frontend already uses GraphQL requests to get the access token.

Side changes:

• Removed unused _download_access_token method.
• Moved TwitchGraphQLBaseIE class to the top after TwitchBaseIE class.
• Added a new _download_base_gql method to make general GraphQL requests and remove repeated https://gql.twitch.tv/gql endpoint strings.

I am open to suggestions for improving the code of this PR.

[dstftw]

Inline.

[galipmedia]

Can anyone here help me? I am trying to hit the endpoint as specified in the code but I am not getting an access token back as the 'value' but rather a json object...

  data: {
    videoPlaybackAccessToken: {
      value: '{"authorization":{"forbidden":false,"reason":""},"chansub":{"restricted_bitrates":[]},"device_id":null,"expires":1610841132,"https_required":true,"privileged":false,"user_id":null,"version":2,"vod_id":1234567}',
      signature: '99aecf120103b0bb375bad907aa17a880c51d3c0',
      __typename: 'PlaybackAccessToken'
    }
  },
  extensions: { durationMilliseconds: 70, requestID: '01EW4N4TJSA64ACG62Q2G6KPZM' }
}

I am using the same Client-ID that was working with the old api.

[TaoziDB]

'value' you got is a string, the same as 'value' from using old API.

[galipmedia]

Aha thanks @TaoziDB it works, i just had to uri encode it for the next call.