* De-dupe item-driven notifications
Update how we query for item-driven notifications to de-dupe them for:
1. mentions
2. replies
3. thread subscriptions
4. user subscriptions
users should recieve only 1 notification for any given item created by another user, following the above priority order
this is accomplished by querying for replies to current user, replies on subscribed threads, items from subscribed users, and mentions (if enabled for the current user), sorting those results by item id and priority order within item id based on notification type, then selecting the highest priority notification from each item id
these results are then union all'ed with all other notification types, unchanged.
* remove extra union hashing
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Co-authored-by: keyan <keyan.kousha+huumn@gmail.com>
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