Clean up references to guest accounts in last_modifier_id

In acc2353 we changed `transferGuestSession` to update
`last_modifier_id` and delete the guest account after all sessions have
been transferred. This upgrade step does a similar thing with existing
sessions. We don't update the modification date because we don't know
when the session was transferred. We also double check that the guest
account doesn't have any sessions associated with it so that we can
safely delete it.

Fixes syslabcom/scrum#2155

src/euphorie/upgrade/deployment/v1/20240423105626_clean_up_last_modifier_id/upgrade.py

@@ -0,0 +1,33 @@
+from euphorie.client.model import Account
+from euphorie.client.model import Session
+from euphorie.client.model import SurveySession
+from ftw.upgrade import UpgradeStep
+
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+class CleanUpLastModifierId(UpgradeStep):
+    """Clean up last_modifier_id."""
+
+    def __call__(self):
+        session = Session()
+        obsolete_guest_users = (
+            session.query(Account, SurveySession)
+            .filter(Account.id == SurveySession.last_modifier_id)
+            .filter(Account.id != SurveySession.account_id)
+            .filter(Account.account_type == "guest")
+        )
+        for guest_user, assessment in obsolete_guest_users:
+            assessment.last_modifier_id = assessment.account_id
+            logger.info("Updated session %s", assessment.id)
+            num_assessments = (
+                session.query(SurveySession)
+                .filter(SurveySession.account_id == guest_user.id)
+                .count()
+            )
+            if num_assessments == 0:
+                session.delete(guest_user)
+                logger.info("Deleted user %s", guest_user.id)