Refactoring

* moves updating of shared access users into Intervention

intervention/models/intervention.py

@@ -284,6 +284,25 @@ class Intervention(BaseObject, ShareableObjectMixin, RecordableObjectMixin, Chec
             )
         return deduction
 
+    def update_sharing_user(self, form):
+        """ Adds a new user with shared access to the intervention
+
+        Args:
+            form (ShareInterventionModalForm): The form holding the data
+
+        Returns:
+
+        """
+        form_data = form.cleaned_data
+
+        keep_accessing_users = form_data["users"]
+        new_accessing_users = list(form_data["user_select"].values_list("id", flat=True))
+        accessing_users = keep_accessing_users + new_accessing_users
+        users = User.objects.filter(
+            id__in=accessing_users
+        )
+        self.share_with_list(users)
+
 
 class InterventionDocument(AbstractDocument):
     """