split most fabric and quilt code into common project

platforms/mixin-common/build.gradle.kts

@@ -15,6 +15,8 @@ loom {
 dependencies {
     shadedApi(project(":common:implementation:base"))
     
+    compileOnly("net.fabricmc:sponge-mixin:${Versions.Fabric.mixin}")
+    
     modImplementation("net.fabricmc:fabric-loader:${Versions.Mod.fabricLoader}")
     
     minecraft("com.mojang:minecraft:${Versions.Mod.minecraft}")

platforms/mixin-common/src/main/java/com/dfsek/terra/mod/ModPlatform.java

@@ -4,8 +4,14 @@ import com.dfsek.tectonic.api.TypeRegistry;
 import com.dfsek.tectonic.api.depth.DepthTracker;
 import com.dfsek.tectonic.api.exception.LoadException;
 
+import com.dfsek.terra.api.handle.ItemHandle;
+import com.dfsek.terra.api.handle.WorldHandle;
 import com.dfsek.terra.mod.config.SpawnSettingsTemplate;
 
+import com.dfsek.terra.mod.handle.MinecraftItemHandle;
+
+import com.dfsek.terra.mod.handle.MinecraftWorldHandle;
+
 import net.minecraft.entity.EntityType;
 import net.minecraft.entity.SpawnGroup;
 import net.minecraft.server.MinecraftServer;
@@ -43,10 +49,15 @@ import com.dfsek.terra.mod.config.SpawnGroupTemplate;
 import com.dfsek.terra.mod.config.SpawnTypeConfig;
 import com.dfsek.terra.mod.util.PresetUtil;
 
+import org.jetbrains.annotations.NotNull;
+
 
 public abstract class ModPlatform extends AbstractPlatform {
     public abstract MinecraftServer getServer();
     
+    private final ItemHandle itemHandle = new MinecraftItemHandle();
+    private final WorldHandle worldHandle = new MinecraftWorldHandle();
+    
     public void registerWorldTypes(BiConsumer<Identifier, WorldPreset> registerFunction) {
         getRawConfigRegistry()
                 .forEach(pack -> PresetUtil.createDefault(pack).apply(registerFunction));
@@ -93,4 +104,14 @@ public abstract class ModPlatform extends AbstractPlatform {
     }
 
     protected abstract BaseAddon getPlatformAddon();
+    
+    @Override
+    public @NotNull WorldHandle getWorldHandle() {
+        return worldHandle;
+    }
+    
+    @Override
+    public @NotNull ItemHandle getItemHandle() {
+        return itemHandle;
+    }
 }