Make TikTok username optional based on scopes set

[Skullbock]

In v2, username can be requested only if user.info.profile scope is set. Instead of forcing the scope, since it's not even in the default list of scopes set in the provider, we could just add the username field if the scope is present.

Closes #1198

[liamseys]

I got approved and added this scope, but I still can't see the username.

[liamseys]

@atymic I debugged this: the username field isn't being passed to the fields list when the scope was added. Was this tested before merging?

[atymic]

@liamseys can you share the scopes you're using in laravel?

[liamseys]

@atymic

return Socialite::driver('tiktok')
            ->scopes(['user.info.basic', 'user.info.profile'])
            ->redirect();

[liamseys]

[liamseys]

array:1 [▼ // vendor/socialiteproviders/tiktok/Provider.php:107
  0 => "user.info.basic"
]

When I print $this->scopes in the Provider.php file, I only see user.info.basic, even though I set more in the scopes method.

[atymic]

It should merge them correctly

Can you show your whole controller? Do you set the scopes also when you call ->user();