Prevent duplicate voting to same discussion

[nanaya]

Forgot a unique index.

Fixes #2923.

Useful stuff:

DB::table('beatmap_discussion_votes')->groupBy(['user_id','beatmap_discussion_id'])->having('count(*)', '>', 1)->selectRaw('count(*), max(id), max(score), min(score), beatmap_discussion_id, user_id')->get();

// clean up
$a = DB::table('beatmap_discussion_votes')->groupBy(['user_id','beatmap_discussion_id'])->having('count(*)', '>', 1)->selectRaw('count(*), max(id), max(score), min(score), beatmap_discussion_id, user_id')->get()->pluck('max(id)')->toArray();
BeatmapDiscussionVote::whereIn('id', $a)->get()->each->delete();
php artisan kudosu:recalculate-discussions-grants

[notbakaneko]

How does the cleanup handle if they're more than 2 duplicates? Are there even any cases with more than 2?

[nanaya]

Just run multiple times.

[nanaya]

The hack isn't supposed to be all that smart