Add user blocking (#29028)

Fixes #17453

This PR adds the abbility to block a user from a personal account or
organization to restrict how the blocked user can interact with the
blocker. The docs explain what's the consequence of blocking a user.

Screenshots:


![grafik](https://github.com/go-gitea/gitea/assets/1666336/4ed884f3-e06a-4862-afd3-3b8aa2488dc6)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ae6d4981-f252-4f50-a429-04f0f9f1cdf1)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ca153599-5b0f-4b4a-90fe-18bdfd6f0b6b)

---------

Co-authored-by: Lauris BH <lauris@nix.lv>

services/user/delete.go

@@ -92,6 +92,8 @@ func deleteUser(ctx context.Context, u *user_model.User, purge bool) (err error)
 		&pull_model.ReviewState{UserID: u.ID},
 		&user_model.Redirect{RedirectUserID: u.ID},
 		&actions_model.ActionRunner{OwnerID: u.ID},
+		&user_model.Blocking{BlockerID: u.ID},
+		&user_model.Blocking{BlockeeID: u.ID},
 	); err != nil {
 		return fmt.Errorf("deleteBeans: %w", err)
 	}