docs: public Ability banUser() {
      return builder()
          .name(BAN)
          .locality(ALL)
          .privacy(ADMIN)
          .input(1)
          .action(ctx -> {
            String username = stripTag(ctx.firstArg());
            int userId = getUserIdSendError(username, ctx);
            String bannedUser;
  
            // Protection from abuse
            if (userId == creatorId()) {
              userId = ctx.user().getId();
              bannedUser = isNullOrEmpty(ctx.user().getUserName()) ? addTag(ctx.user().getUserName()) : shortName(ctx.user());
            } else {
              bannedUser = addTag(username);
            }
  
            Set<Integer> blacklist = blacklist();
            if (blacklist.contains(userId))
              sendMd(ABILITY_BAN_FAIL, ctx, escape(bannedUser));
            else {
              blacklist.add(userId);
              sendMd(ABILITY_BAN_SUCCESS, ctx, escape(bannedUser));
            }
          })
          .post(commitTo(db))
          .build();
    }