* Store view counts & last viewed time
* Schedule updating user recommendations. Compute using tf-idf.
* Update contract's lastBetTime and lastCommentTime on new bets and comments.
* Remove contract's lastUpdatedTime
* Remove folds activity feed
* Implement getFeed cloud function
* Hook up client to use getFeed
* Script to cache viewCounts and lastViewTime
* Batched wait all userRecommendations
* Cache view script runs on all users
* Update user feed each hour and get feed from cache doc.
* Delete view cache script
* Update feed script
* Tweak feed algorithm
* Compute recommendation scores from updateUserFeed
* Disable lastViewedScore factor
* Update lastCommentTime script
* Comment out console.log
* Fix timeout issue by calling new cloud functions with part of the work.
* Listen for contract updates to feed.
* Handle new user: use default feed of top markets this week
* Track lastUpdatedTime
* Tweak logic of calling cloud functions in batches
* Tweak cloud function batching
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