title: DefaultSocialAccountAdapter overrriding pre_social_login
body: <p>I'm trying to verify email address before login or singup via google account.</p>
  
  <p>I have below code:</p>
  
  <pre><code>from django.http import Http404
  from allauth.socialaccount.adapter import DefaultSocialAccountAdapter
  
  class MySocialAccountAdapter(DefaultSocialAccountAdapter):
  
  def pre_social_login(self, request, sociallogin):
      email_domain = sociallogin.account.user.email.split('@')[1].lower()
      if email_domain == 'mysuperdomain.org':
          print email_domain
          pass
  </code></pre>
  
  <p>It is working fine when I'm login(google account already exist in Django) but when trying first time singup i have err below:</p>
  
  <p>RelatedObjectDoesNotExist at /accounts/google/login/callback/
  SocialAccount has no user.</p>
  
  <p>Any wisdom will be most appreciated.</p>
  
  <p>Thanks,</p>
  
  <p>J</p>
  
  <p>ok have some progress with below signal code:</p>
  
  <pre><code>    from allauth.account.signals import user_signed_up
      from django.http import Http404
      from auth.settings import ALLOWED_DOMAIN
  
  
      def email_allowed(user, **kwargs):
          email_domain = user.email.split('@')[1].lower()
          if not email_domain == ALLOWED_DOMAIN:
              raise Http404
  
      user_signed_up.connect(email_allowed)
  </code></pre>
  
  <p>but still need to take some action to prevent adding user account when domain is not allowed.</p>