Add mute command, command usages and smaller improvements

src/main/java/de/shiewk/smoderation/util/PlayerUtil.java

@@ -2,15 +2,31 @@ package de.shiewk.smoderation.util;
 
 import org.bukkit.Bukkit;
 import org.bukkit.OfflinePlayer;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.UUID;
 
 public abstract class PlayerUtil {
     private PlayerUtil(){}
 
-    public static String offlinePlayerName(UUID uuid){
+    public static final UUID UUID_CONSOLE = new UUID(0, 0);
+
+    public static @NotNull String offlinePlayerName(UUID uuid){
+        if (uuid.equals(UUID_CONSOLE)){
+            return "UUID_CONSOLE";
+        }
         OfflinePlayer player = Bukkit.getOfflinePlayer(uuid);
         return player.getName() == null ? uuid.toString() : player.getName();
     }
 
+    public static @Nullable UUID offlinePlayerUUIDByName(String name){
+        final OfflinePlayer offlinePlayer = Bukkit.getOfflinePlayerIfCached(name);// getOfflinePlayerIfCached(String) is safer (I have experience with getOfflinePlayer(String) returning wrong UUIDs)
+        if (offlinePlayer != null) {
+            return offlinePlayer.getUniqueId();
+        } else {
+            return null;
+        }
+    }
+
 }