Change algorithm of follow recommendations

[Gargron]

Replace "past interactions" algorithm with "friends of friends" while respecting the "show follows and followers" and "feature profile in discovery algorithms" privacy settings. Cleans up a lot of the code surrounding follow recommendations. We can avoid maintaining sorted sets per language for global follow recommendations in Redis when the materialized view query is fast enough.

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Fixes MAS-171

[codecov]

Codecov Report

Attention: 15 lines in your changes are missing coverage. Please review.

Comparison is base (8b1eeb2) 83.67% compared to head (c012e5f) 83.70%.
Report is 5 commits behind head on main.

❗ Current head c012e5f differs from pull request most recent head 7e19344. Consider uploading reports for the commit 7e19344 to get more accurate results

Files	Patch %	Lines
...els/account_suggestions/similar_profiles_source.rb	57.89%	8 Missing ⚠️
app/controllers/api/v2/suggestions_controller.rb	71.42%	2 Missing ⚠️
app/models/account_suggestions.rb	93.75%	0 Missing and 1 partial ⚠️
...s/account_suggestions/friends_of_friends_source.rb	83.33%	1 Missing ⚠️
app/models/concerns/account/search.rb	0.00%	0 Missing and 1 partial ⚠️
app/models/follow_recommendation_filter.rb	50.00%	1 Missing ⚠️
app/services/account_search_service.rb	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #28314      +/-   ##
==========================================
+ Coverage   83.67%   83.70%   +0.02%     
==========================================
  Files        1038     1039       +1     
  Lines       28255    28221      -34     
  Branches     4555     4549       -6     
==========================================
- Hits        23642    23622      -20     
+ Misses       3485     3470      -15     
- Partials     1128     1129       +1     

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[ClearlyClaire]

This seems sensible overall, but I have a hard time evaluating the actual algorithms. On my single-user instance:

• AccountSuggestions::FriendsOfFriendsSource does not return a single suggestion
• AccountSuggestions::SimilarProfilesSource does return suggestions, but no one I would follow if I weren't following them already (as pointed out in inline comments, the must_not_clauses filtering them out are not actually used in the final query)

From my own perspective (single-user server with around 250 follows), those recommendations perform worse than the existing ones in that it doesn't recommend people I would actually consider following. That being said, I do not use this feature either way.

Also, this PR requires re-indexing accounts, this needs to be mentioned.

[ClearlyClaire]

In addition to the inline comment, there's an API design issue I'm wondering about: the API returns, along with suggestions, which source they're from. However, there is no way to select or filter them, which makes the source classification much less useful imho.

[Gargron]

The source is not intended to filter, but to provide transparency about why a suggestion appears.

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[github-actions]

This pull request has resolved merge conflicts and is ready for review.

[ClearlyClaire]

Seems fine overall, although I'm still not sure about the quality of the recommendations, especially on small servers.

Also, this requires re-indexing accounts for the “similar profiles” source to work, we'll need to remember to add that to the release notes.

[vmstan]

Seems fine overall, although I'm still not sure about the quality of the recommendations, especially on small servers.

Also, this requires re-indexing accounts for the “similar profiles” source to work, we'll need to remember to add that to the release notes.

Is this re-indexing in ES or something else?

[ClearlyClaire]

ES. You need to run tootctl search deploy --only=accounts basically

[outlaw-dame]

I do believe for minorities that have opted into discovery, there should be a bump that allows those accounts better options to be found.

[ocdtrekkie]

@outlaw-dame I don't have an issue with this, but I suspect the implementation would be messy. Presumably you'd either need to skim profile data for specific keywords you wanted to bump, or you'd need to add profile options for users to self-claim that they should be included (which would need to be federated, since you don't want to only recommend local users). I'm guessing it would probably be preferable to base it on profile data so there isn't a check box people can just check for growth hacking, but then someone would need to maintain a list of key words or phrases that should trigger such a bump.

[tribela]

Blocked persons(individual block + server block) are listed on follow suggestion by "friends_of_friends"