docs: update details on retrieving nested categories (#10317)

www/apps/resources/app/storefront-development/products/categories/nested-categories/page.mdx

@@ -8,7 +8,11 @@ export const metadata = {
 
 A product category has parent and child categories.
 
-To retrieve the child or nested categories of a category in your storefront, pass `*category_children` to the `fields` query parameter of the [Get a Category API Route](!api!/store#product-categories_getproductcategoriesid).
+To retrieve the child or nested categories of a category in your storefront, pass to the [Get a Category API Route](!api!/store#product-categories_getproductcategoriesid) the following query parameters:
+
+- `include_descendants_tree=true` to retrieve each category's nested categories at all levels.
+- Add `category_children` to `fields`, which is the field that will hold a category's nested categories. You can either pass `*category_children` to retrieve all fields of a child category, or specify the fields specifically to avoid a large response size. For example, `field=category_children.id,category_children.name`.
+- `parent_category_id=null` to retrieve only the categories that don't have a parent. This avoids retrieving the child categories multiple times in the response since child categories are now set in their parent's object.
 
 For example:
 
@@ -16,12 +20,16 @@ For example:
   <CodeTab label="Fetch API" value="fetch">
 
 export const fetchHighlights = [
-  ["2", `"*category_children"`, "Select the `category_children` relation."],
+  ["2", `"category_children.id,category_children.name"`, "Select the fields of category children"],
+  ["3", `"include_descendants_tree"`, "Indicate that all nested categories should be retrieved."],
+  ["4", "parent_category_id", "Since each category will have its children, you only retrieve categories that don't have a parent."]
 ]
 
   ```ts highlights={fetchHighlights}
   const searchParams = new URLSearchParams({
-    fields: "*category_children",
+    fields: "category_children.id,category_children.name",
+    include_descendants_tree: true,
+    parent_category_id: null
   })
 
   fetch(`http://localhost:9000/store/product-categories/${id}?${
@@ -44,10 +52,11 @@ export const fetchHighlights = [
 
 export const highlights = [
   ["12", "{ params: { id } }: Params", "This is based on Next.js which passes the path parameters as a prop."],
-  ["24", `"*category_children"`, "Select the `category_children` relation."],
-  ["27"], ["28"], ["29"], 
-  ["30"], ["31"], ["32"], ["33"], ["34"], ["35"], ["36"], ["37"], ["38"], ["39"],
-  ["53", "", "Show the nested categories."],
+  ["24", `"category_children.id,category_children.name"`, "Select the fields of category children"],
+  ["25", "parent_category_id", "Since each category will have its children, you only retrieve categories that don't have a parent."]
+  ["26"], ["27"], ["28"], 
+  ["29"], ["30"], ["31"], ["32"], ["33"], ["34"], ["35"], ["36"], ["37"], ["38"],
+  ["54", "", "Show the nested categories."],
 ]
 
   ```tsx highlights={highlights}
@@ -74,7 +83,8 @@ export const highlights = [
       }
 
       const searchParams = new URLSearchParams({
-        fields: "*category_children",
+        fields: "category_children.id,category_children.name",
+        parent_category_id: null
       })
 
       fetch(`http://localhost:9000/store/product-categories/${id}?${