feat(ban): Implementing ban.

Rough code, not based on permission.

src/main/java/emu/grasscutter/command/commands/UnBanCommand.java

@@ -0,0 +1,66 @@
+package emu.grasscutter.command.commands;
+
+import java.util.List;
+
+import emu.grasscutter.Grasscutter;
+import emu.grasscutter.command.Command;
+import emu.grasscutter.command.CommandHandler;
+import emu.grasscutter.database.DatabaseHelper;
+import emu.grasscutter.game.Account;
+import emu.grasscutter.game.player.Player;
+
+import static emu.grasscutter.utils.Language.translate;
+
+@Command(
+    label = "unban",
+    usage = "unban <player>",
+    description = "commands.unban.description",
+    targetRequirement = Command.TargetRequirement.NONE
+)
+public final class UnBanCommand implements CommandHandler {
+
+    private boolean unBanAccount(int uid) {
+        Player player = Grasscutter.getGameServer().getPlayerByUid(uid, true);
+
+        if (player == null) {
+            return false;
+        }
+
+        Account account = player.getAccount();
+
+        if (account == null) {
+            account = DatabaseHelper.getAccountByPlayerId(uid);
+        }
+
+        account.setBanReason(null);
+        account.setBanEndTime(0);
+        account.setBanStartTime(0);
+        account.setBanned(false);
+        account.save();
+
+        return true;
+    }
+
+    @Override
+    public void execute(Player sender, Player targetPlayer, List<String> args) {
+        if (args.size() < 1) {
+            CommandHandler.sendMessage(sender, translate(sender, "commands.unban.command_usage"));
+            return;
+        }
+
+        int uid = 0;
+
+        try {
+            uid = Integer.parseInt(args.get(0));
+        } catch (NumberFormatException ignored) {
+            CommandHandler.sendMessage(sender, translate(sender, "commands.unban.invalid_player_id"));
+            return;
+        }
+
+        if (unBanAccount(uid)) {
+            CommandHandler.sendMessage(sender, translate(sender, "commands.unban.success"));
+        } else {
+            CommandHandler.sendMessage(sender, translate(sender, "commands.unban.failure"));
+        }
+    }
+}