Prior to this fix, in the production rails console we ran the following:
```ruby
Articles::Feeds::WeightedQueryStrategy
.new(user: nil, page: 1, tags: nil)
.featured_story_and_default_home_feed(user_signed_in: false)
```
The result was: `[nil, []]`. Which in the
[StoriesController#assign_feed_stories][1] is where we have the
following:
```ruby
@featured_story, @stories = feed
.featured_story_and_default_home_feed(
user_signed_in: user_signed_in?)
```
In Blazer, I ran the following query at 2021-12-02 Thu 20:41 EST:
```sql
SELECT * FROM articles
WHERE featured = true
AND published = true
AND published_at > (NOW() - interval '7 days')
AND published_at < NOW()
AND main_image IS NOT NULL
```
So the logic of filtering with `only_featured` resulted in the
`@featured_story` being `nil`. Which then cascaded into the logic for
determining the remainder of the results.
For further discussion see the inline comments and specs that I wrote.
In addition to the above, I'm also reusing
`Articles::Feeds::FindFeaturedStory`
Prior to this commit, the `Articles::Feeds::WeightedQueryStrategy` first
grabbed the featured story, then grabbed the remaining articles. This
is different than the implementation of the
`Articles::Feeds::LargeForemExperimental` in which we first grab all the
articles then claim one as the featured.
In the WeightedQueryStrategy, the articles would not include the
featured. However, in the LargeForemExperimental it would. This
results in upstream logic in [app/javascript/articles/Feed.jsx][2]
going through and removing one of the articles.
[1]:c1a3ba99eb/app/controllers/stories_controller.rb (L237-L271)
[2]:c1a3ba99eb/app/javascript/articles/Feed.jsx (L57-L63)
* Fixing weighted query hotness grab logic
Prior to this commit, I carried over (albeit imprecisely) logic from the
LargeForemExperimental. That logic was to help limit articles to those
that were published since the user's latest page view.
However, I introduced a bug in this transcription. Now both
LargeForemExperimental and WeightedQueryStrategy use the same logic to
determine the oldest publication date to search for in the feed.
This resolves a bug reported where users were not seeing a large number
of items in their feed.
Incidentally, if a forem has little activity in the 18 hours, there
might be very few items in the feed.
I believe, going forward, we may need to better parameterize how many
hours is considered "stale since last page view".
Related to #15240
* Fixing implementation detail
* Extracting helper method
Prior to this commit, I had introduced a method an put it in a less
ideal module space. This commit extracts that method to a more readily
shareable module space.
I've added a few more specs to help clarify and verify behavior.
* Updating documentation
* Renaming and documenting variables/constants
* Fixing that which I broke
