use preferred_username and fallback to name

pandora/app/oidc.py

@@ -12,7 +12,11 @@ User = get_user_model()
 class OIDCAuthenticationBackend(mozilla_django_oidc.auth.OIDCAuthenticationBackend):
     def create_user(self, claims):
         user = super(OIDCAuthenticationBackend, self).create_user(claims)
-        username = claims.get("preferred_username")
+        username = None
+        for key in ('preferred_username', 'name'):
+            if claims.get(key):
+                username = claims[key]
+                break
         n = 1
         if username and username != user.username:
             uname = username