Support multiple channels

[tzarebczan]

Right now a user authenticates to a single channel, and no matter what channel they select in the LBRY app, it will mirror it to youtube . It should be linked to the LBRY channel.

[tiger5226]

To support this we will need the following tasks completed:

• We show the channel name its tied to in the app when they are already authenticated.
• We provide a sign out button, so they can re-signin to choose a different channel.

[tiger5226]

I cannot get the channel name. That apparently requires an escalated scope. When we upload the video, the returned information does have the channel title in the response. However, when we check if we already have authorization, we are not allowed to access the channel list that the user has unless we request a more wide ranging scope.

We can request re-verification and get the youtube.readonly scope added, but that is a process. This gives us access to their whole youtube account and all the information associated with it(channel list).

So for now added the signup, and unlink button. So someone could always unlink and link the channel they want.

[tzarebczan]

My main point of confusion is that they may try to select a different LBRY channel but the youtube sync will always upload to the one they linked. Maybe we can just make this clearer in the UI.