Just had an idea, we could refactor this to something like:

~~~ruby
def create
  link_youtube or login_with_auth or verify_auth or register_with_auth
end

...

private

def link_youtube
  if omniauth_params_for_youtube
    ...
    return true
  else
    return false
  end
end

def login_with_auth
  if Authentication.find_by_provider_and_uid(...)
    ...
    return true
  else
    return false
  end
end

def verify_auth
  if current_user
    ...
    return true
  else
    return false
  end
end

def register_with_auth
  ...
  return true
end
~~~

let me know what you think about this approach