Open WebUI: Inconsistent authorization controls within memories API

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.6.19, authorization controls surrounding the memories API were inconsistent, resulting in the ability of a standard user to delete, restore, and view the contents of other users' memories. Using a newly created non-admin user with no existing memories, it is possible to view existing memories via POST /api/v1/memories/query. Similarly, even if a non-admin user cannot modify another user's memory data via POST /api/v1/memories/{memory_id}/update, the endpoint's response improperly leaks the content of that memory if a valid memory_id is known. The DELETE /api/v1/memories/{memory_id} can also be used by any user to delete an existing memory. Deleted memories can then be restored by calling the POST /api/v1/memories/{memory_id}/update endpoint again. This vulnerability is fixed in 0.6.19.