title: Django allauth - Multiple social accounts with a custom user
body: <p>I've been trying to find how to add a new social account to a user that has already signed up and loged in, using <code>django-allauth</code>. So far, I have found <a href="https://stackoverflow.com/questions/13140021/django-allauth-linking-multiple-social-accounts-to-a-single-user">this question</a>, and <a href="https://stackoverflow.com/questions/13037644/how-do-i-connect-multiple-social-auth-providers-to-the-same-django-user-using-dj">this other question</a> related to what I need, but what is suggested doesn't work.</p>
  
  <p>I'm using a custom User class, which authenticates through email, and once I have the first social account successfully created, it wont let me add another one. I've tried putting the <code>provider_login_url</code> in a page where the user is authenticated, as suggested in one of the mentioned answers, but it seems to do logout and then try to sign up again, but then, as the email is the same, "it clashes with the email of an existing user".</p>
  
  <p>How can I get the expected behavior? which is, that <code>django-allauth</code> recognize the email as belonging to an existing user, and therefore creating only a new <code>socialaccount</code>, and not a new user.</p>