docs: fix details on setting / updating customer ID in cart (#9689)

Author: shahednasser

www/apps/resources/app/storefront-development/cart/create/page.mdx

@@ -117,24 +117,8 @@ This is necessary, as only products matching the cart's sales channel(s) can be
 
 ## Associate Customer with Cart
 
-When creating the cart, you can associate the logged-in customer's ID with the cart by passing a `customer_id` request body parameter.
+When the cart is created for a logged-in customer, it's automatically associated with that customer.
 
-For example:
-
-export const customerHighlights = [
-  ["5", "customer.id", "Assuming you have the customer object."]
-]
+If the customer is a guest, then later logs in, you can set their ID on the cart by updating it.
 
-```ts highlights={customerHighlights}
-fetch(`http://localhost:9000/store/carts`, {
-  // ...
-  body: JSON.stringify({
-    // ...
-    customer_id: customer.id,
-  }),
-})
-.then((res) => res.json())
-.then(({ cart }) => {
-  localStorage.setItem("cart_id", cart.id)
-})
-```
+Refer to [this documentation](../update/page.mdx#update-carts-customer) to learn how to set the customer of a cart.

www/apps/resources/app/storefront-development/cart/update/page.mdx

@@ -53,6 +53,12 @@ The Update Cart API route accepts a `region_id` request body parameter, whose va
 
 If a guest customer logs in, you must update the cart to be associated with the logged-in customer.
 
+<Note>
+
+You can't change the `customer_id` if the cart was associated with a customer previously.
+
+</Note>
+
 For example:
 
 export const updateCustomerHighlights = [

www/apps/resources/generated/edit-dates.mjs

@@ -152,10 +152,10 @@ export const generatedEditDates = {
   "app/service-factory-reference/tips/filtering/page.mdx": "2024-07-31T17:01:33+03:00",
   "app/service-factory-reference/page.mdx": "2024-07-26T14:40:56+00:00",
   "app/storefront-development/cart/context/page.mdx": "2024-09-11T10:08:05.194Z",
-  "app/storefront-development/cart/create/page.mdx": "2024-09-11T10:08:05.195Z",
+  "app/storefront-development/cart/create/page.mdx": "2024-10-21T07:40:27.947Z",
   "app/storefront-development/cart/manage-items/page.mdx": "2024-09-11T10:10:54.932Z",
   "app/storefront-development/cart/retrieve/page.mdx": "2024-09-11T10:12:55.828Z",
-  "app/storefront-development/cart/update/page.mdx": "2024-09-11T10:12:47.704Z",
+  "app/storefront-development/cart/update/page.mdx": "2024-10-21T07:41:21.046Z",
   "app/storefront-development/cart/page.mdx": "2024-06-11T11:56:37+03:00",
   "app/storefront-development/checkout/address/page.mdx": "2024-09-11T09:40:02.899Z",
   "app/storefront-development/checkout/complete-cart/page.mdx": "2024-09-11T09:40:48.531Z",