Drop legacy user session tables (#12675)

src/backend/InvenTree/users/migrations/0016_remove_legacy_user_sessions_table.py

@@ -0,0 +1,27 @@
+"""Remove the orphaned 'user_sessions_session' table.
+
+Instances upgraded from a version predating #6293 (which switched from the
+django-user-sessions package to allauth.usersessions) can still have the old
+'user_sessions_session' table in their database. As the 'user_sessions' app
+was removed from INSTALLED_APPS, Django no longer knows about this table or
+its foreign key to auth_user, so deleting a user with an old-style session
+fails with a ForeignKeyViolation. Drop the leftover table if present.
+"""
+
+from django.db import migrations
+
+
+def remove_legacy_table(apps, schema_editor):
+    """Drop the legacy 'user_sessions_session' table, if it exists."""
+    table_name = 'user_sessions_session'
+
+    if table_name in schema_editor.connection.introspection.table_names():
+        schema_editor.execute(f'DROP TABLE {table_name}')
+
+
+class Migration(migrations.Migration):
+    dependencies = [('users', '0015_alter_userprofile_type')]
+
+    operations = [
+        migrations.RunPython(remove_legacy_table, reverse_code=migrations.RunPython.noop)
+    ]