Bug: leak in username sorted set

[SHAcollision]

It looks like the same pubky_id could show up twice in the Sorted:Users:Name Sorted Set. As far as I remember, users that changed their username used to be a problem (they duplicated in this sorted set), but we fixed this. In any case, there seems to be still some ways a user could end up showing more than once under different usernames in this Sorted Set, needs debugging, possibly changing your username under some scenario can still trigger this.

Another case:

And case here

Searching for "`jo" should not yield a result anymore, since John changed his username to remove the quote marking. Yet it does

I have manually cleaned up the production database and I deleted:

• 4 instances of duplicated user_id in the sorted set
• 1 instance of a non-existing user anymore still existing in this sorted set.