feat(logindata/oauth): add email field

jdav_web/logindata/oauth.py

@@ -6,6 +6,8 @@ class CustomOAuth2Validator(OAuth2Validator):
     # otherwise the OIDC standard scopes are used.
 
     def get_additional_claims(self, request):
-        return {
+        if request.user.member:
-            "preferred_username": request.user.username
+            context = {'email': request.user.member.email}
-        }
+        else:
+            context = {}
+        return dict(context, preferred_username=request.user.username)