Added: Item association model

src/models/ItemAssociation.js

@@ -0,0 +1,25 @@
+const mongoose = require("mongoose");
+
+const schema = new mongoose.Schema(
+  {
+    item_id: {
+      type: mongoose.Schema.Types.ObjectId,
+      ref: "Item",
+    },
+    sub_level_id: {
+      type: mongoose.Schema.Types.ObjectId,
+      ref: "Sublevel",
+    },
+    quantity: {
+      type: Number,
+      default: 0,
+    },
+  },
+  {
+    timestamps: true,
+  }
+);
+
+const ItemAssociation = mongoose.model("ItemAssociation", schema);
+
+module.exports = ItemAssociation;