Report user accounts

[MrKaplan-lw]

Requirements

• Is this a feature request? For questions or discussions use https://lemmy.ml/c/lemmy_support
• Did you check to see if this issue already exists?
• Is this only a feature request? Do not put multiple feature requests in one issue.
• Is this a backend issue? Use the lemmy-ui repo for UI / frontend issues.
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Is your proposal related to a problem?

Spam accounts frequently fly under the radar of admins of the instance they're based on due to reports being resolved as their spam posts/comments are removed.
I recently started reporting posts and comments of spammers before removing them through instance/community bans to hopefully make them visible to their home instance admins, but this will soon no longer be a feasible workaround when #5344 gets merged.
Additionally, spammers sometimes only have spam in their profile descriptions and only trigger some actions that cause their profile to federate but they won't have any content that could get reported.

Describe the solution you'd like.

Users can report other users.
Reports should be sent to the reported user's home instance admins.

Describe alternatives you've considered.

Attempt to identify remote instance admins and send them private messages.
This is not a feasible solution as this would require determining remote instance software and use software specific APIs.
There is also no way to have a shared report queue among admins, so each admin will have to review each message individually.

Additional context

No response

[dessalines]

@dullbananas recently added community reporting, I spose we could add the same for users. I'm pretty swamped rn with other things tho, I'd appreciate it if someone else could handle.