✨(backend) allow to create a new user in a marketing system

We want to create a new user in a marketing system to create a dedicated
onboarding for each of them. The marketing service is implemented in the
django-lasuite library and it is possible to pick the backend we want
or implement a new one following the documentation on this library.

src/backend/core/authentication/backends.py

@@ -6,6 +6,7 @@ import os
 from django.conf import settings
 from django.core.exceptions import SuspiciousOperation
 
+from lasuite.marketing.tasks import create_or_update_contact
 from lasuite.oidc_login.backends import (
     OIDCAuthenticationBackend as LaSuiteOIDCAuthenticationBackend,
 )
@@ -57,3 +58,22 @@ class OIDCAuthenticationBackend(LaSuiteOIDCAuthenticationBackend):
             return self.UserModel.objects.get_user_by_sub_or_email(sub, email)
         except DuplicateEmailError as err:
             raise SuspiciousOperation(err.message) from err
+
+    def post_get_or_create_user(self, user, claims, is_new_user):
+        """
+        Post-processing after user creation or retrieval.
+
+        Args:
+          user (User): The user instance.
+          claims (dict): The claims dictionary.
+          is_new_user (bool): Indicates if the user was newly created.
+
+        Returns:
+        - None
+
+        """
+
+        if is_new_user and settings.SIGNUP_NEW_USER_TO_MARKETING_EMAIL:
+            create_or_update_contact.delay(
+                email=user.email, attributes={"DOCS_SOURCE": ["SIGNIN"]}
+            )