Remove old config & migrate legacy configs

src/main/java/emu/grasscutter/Configuration.java

 package emu.grasscutter;
 
+import com.google.gson.JsonObject;
 import emu.grasscutter.Grasscutter.*;
 import emu.grasscutter.game.mail.Mail.*;
 
+import java.io.FileReader;
 import java.lang.reflect.Field;
 import java.util.Arrays;
 import java.util.Locale;
@@ -24,7 +26,16 @@ public final class Configuration {
      * Attempts to update the server's existing configuration to the latest configuration.
      */
     public static void updateConfig() {
-        var existing = config.version; 
+        try { // Check if the server is using a legacy config.
+            JsonObject configObject = Grasscutter.getGsonFactory()
+                    .fromJson(new FileReader(Grasscutter.configFile), JsonObject.class);
+            if(!configObject.has("version")) {
+                Grasscutter.getLogger().info("Updating legacy configuration...");
+                Grasscutter.saveConfig(null);
+            }
+        } catch (Exception ignored) { }
+        
+        var existing = config.version;
         var latest = version();
         
         if(existing == latest) 

src/main/java/emu/grasscutter/Grasscutter.java

@@ -43,7 +43,7 @@ public final class Grasscutter {
 	private static Language language;
 
 	private static final Gson gson = new GsonBuilder().setPrettyPrinting().create();
-	private static final File configFile = new File("./config.json");
+	public static final File configFile = new File("./config.json");
 
 	private static int day; // Current day of week.
 
@@ -60,6 +60,8 @@ public final class Grasscutter {
 
 		// Load server configuration.
 		config = Grasscutter.loadConfig();
+		// Attempt to update configuration.
+		Configuration.updateConfig();
 
 		// Load translation files.
 		Grasscutter.loadLanguage();

src/main/java/emu/grasscutter/utils/Utils.java

@@ -11,7 +11,6 @@ import java.util.Map;
 import java.util.Random;
 import java.util.Locale;
 
-import emu.grasscutter.Config;
 import emu.grasscutter.Configuration;
 import emu.grasscutter.Grasscutter;
 import io.netty.buffer.ByteBuf;