chore: drop related name on base model created_by_user

This caused, for example, on the `User` model to set an `acl`
attribute, pointing to the creator.

This is very confusing, for example if searching for all users within a scope:

>>> User.objects.filter(acl__scope__in=scope_list)

This would return the user who has *created* all those ACLs, instead of the
users who are in fact *granted* the ACL.

The correct way would have been

>>> User.objects.filter(acls__scope__in=scope_list)

So to avoid this confusion (and others), we'll remove the related name.

emeis/core/models.py

@@ -36,7 +36,9 @@ def get_language_code():
 class BaseModel(models.Model):
     created_at = models.DateTimeField(auto_now_add=True, db_index=True)
     modified_at = models.DateTimeField(auto_now=True, db_index=True)
-    created_by_user = models.ForeignKey("User", null=True, on_delete=models.SET_NULL)
+    created_by_user = models.ForeignKey(
+        "User", null=True, on_delete=models.SET_NULL, related_name="+"
+    )
     metainfo = models.JSONField(_("metainfo"), default=dict)
 
     class Meta: