events: ensure all models' __str__ can be called without any further lookups (#9480)

* events: ensure all models' __str__ can be called without any further lookups

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* allow for additional queries for models using default_token_key

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

---------

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

authentik/core/models.py

@@ -632,7 +632,7 @@ class UserSourceConnection(SerializerModel, CreatedUpdatedModel):
         raise NotImplementedError
 
     def __str__(self) -> str:
-        return f"User-source connection (user={self.user.username}, source={self.source.slug})"
+        return f"User-source connection (user={self.user_id}, source={self.source_id})"
 
     class Meta:
         unique_together = (("user", "source"),)