chore(): Reorganize modules (#7210)

**What**
Move all modules to the modules directory

packages/modules/order/src/utils/actions/shipping-add.ts

@@ -0,0 +1,46 @@
+import { MedusaError, isDefined } from "@medusajs/utils"
+import { ChangeActionType } from "../action-key"
+import { OrderChangeProcessing } from "../calculate-order-change"
+
+OrderChangeProcessing.registerActionType(ChangeActionType.SHIPPING_ADD, {
+  operation({ action, currentOrder }) {
+    const shipping = Array.isArray(currentOrder.shipping_methods)
+      ? currentOrder.shipping_methods
+      : [currentOrder.shipping_methods]
+
+    shipping.push({
+      id: action.reference_id!,
+      price: action.amount as number,
+    })
+
+    currentOrder.shipping_methods = shipping
+  },
+  revert({ action, currentOrder }) {
+    const shipping = Array.isArray(currentOrder.shipping_methods)
+      ? currentOrder.shipping_methods
+      : [currentOrder.shipping_methods]
+
+    const existingIndex = shipping.findIndex(
+      (item) => item.id === action.reference_id
+    )
+
+    if (existingIndex > -1) {
+      shipping.splice(existingIndex, 1)
+    }
+  },
+  validate({ action }) {
+    if (!action.reference_id) {
+      throw new MedusaError(
+        MedusaError.Types.INVALID_DATA,
+        "Reference ID is required."
+      )
+    }
+
+    if (!isDefined(action.amount)) {
+      throw new MedusaError(
+        MedusaError.Types.INVALID_DATA,
+        "Amount is required."
+      )
+    }
+  },
+})